Add identifier tags in comments to work around scaladocs bug

The bug is that annotations and comments cannot both be displayed in the
summary page. The workaround is adding a special pattern that we grep for
as we post-process the DOM tree in JavaScript.

Example: A @DeveloperAPI annotated class's comment must begin with
":: Developer API ::"

Author: andrewor14

core/src/main/scala/org/apache/spark/Aggregator.scala

@@ -21,6 +21,7 @@ import org.apache.spark.annotations.DeveloperAPI
 import org.apache.spark.util.collection.{AppendOnlyMap, ExternalAppendOnlyMap}
 
 /**
+ * :: DeveloperAPI ::
  * A set of functions used to aggregate data.
  *
  * @param createCombiner function to create the initial value of the aggregation.

core/src/main/scala/org/apache/spark/Dependency.scala

@@ -22,13 +22,15 @@ import org.apache.spark.rdd.RDD
 import org.apache.spark.serializer.Serializer
 
 /**
+ * :: DeveloperAPI ::
  * Base class for dependencies.
  */
 @DeveloperAPI
 abstract class Dependency[T](val rdd: RDD[T]) extends Serializable
 
 
 /**
+ * :: DeveloperAPI ::
  * Base class for dependencies where each partition of the parent RDD is used by at most one
  * partition of the child RDD.  Narrow dependencies allow for pipelined execution.
  */
@@ -44,6 +46,7 @@ abstract class NarrowDependency[T](rdd: RDD[T]) extends Dependency(rdd) {
 
 
 /**
+ * :: DeveloperAPI ::
  * Represents a dependency on the output of a shuffle stage.
  * @param rdd the parent RDD
  * @param partitioner partitioner used to partition the shuffle output
@@ -63,6 +66,7 @@ class ShuffleDependency[K, V](
 
 
 /**
+ * :: DeveloperAPI ::
  * Represents a one-to-one dependency between partitions of the parent and child RDDs.
  */
 @DeveloperAPI
@@ -72,6 +76,7 @@ class OneToOneDependency[T](rdd: RDD[T]) extends NarrowDependency[T](rdd) {
 
 
 /**
+ * :: DeveloperAPI ::
  * Represents a one-to-one dependency between ranges of partitions in the parent and child RDDs.
  * @param rdd the parent RDD
  * @param inStart the start of the range in the parent RDD

core/src/main/scala/org/apache/spark/FutureAction.scala

@@ -26,6 +26,7 @@ import org.apache.spark.rdd.RDD
 import org.apache.spark.scheduler.{JobFailed, JobSucceeded, JobWaiter}
 
 /**
+ * :: Experimental ::
  * A future for the result of an action to support cancellation. This is an extension of the
  * Scala Future interface to support cancellation.
  */
@@ -86,6 +87,7 @@ trait FutureAction[T] extends Future[T] {
 
 
 /**
+ * :: Experimental ::
  * A [[FutureAction]] holding the result of an action that triggers a single job. Examples include
  * count, collect, reduce.
  */
@@ -151,6 +153,7 @@ class SimpleFutureAction[T] private[spark](jobWaiter: JobWaiter[_], resultFunc:
 
 
 /**
+ * :: Experimental ::
  * A [[FutureAction]] for actions that could trigger multiple Spark jobs. Examples include take,
  * takeSample. Cancellation works by setting the cancelled flag to true and interrupting the
  * action thread if it is being blocked by a job.

core/src/main/scala/org/apache/spark/Logging.scala

@@ -24,6 +24,7 @@ import org.slf4j.impl.StaticLoggerBinder
 import org.apache.spark.annotations.DeveloperAPI
 
 /**
+ * :: DeveloperAPI ::
  * Utility trait for classes that want to log data. Creates a SLF4J logger for the class and allows
  * logging messages at different levels using methods that only evaluate parameters lazily if the
  * log level is enabled.

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -49,6 +49,7 @@ import org.apache.spark.ui.SparkUI
 import org.apache.spark.util.{ClosureCleaner, MetadataCleaner, MetadataCleanerType, TimeStampedHashMap, Utils}
 
 /**
+ * :: DeveloperAPI ::
  * Main entry point for Spark functionality. A SparkContext represents the connection to a Spark
  * cluster, and can be used to create RDDs, accumulators and broadcast variables on that cluster.
  *
@@ -65,6 +66,7 @@ class SparkContext(config: SparkConf) extends Logging {
   private[spark] var preferredNodeLocationData: Map[String, Set[SplitInfo]] = Map()
 
   /**
+   * :: DeveloperAPI ::
    * Alternative constructor for setting preferred locations where Spark will create executors.
    *
    * @param preferredNodeLocationData used in YARN mode to select nodes to launch containers on. Ca
@@ -716,6 +718,7 @@ class SparkContext(config: SparkConf) extends Logging {
   }
 
   /**
+   * :: DeveloperAPI ::
    * Register a listener to receive up-calls from events that happen during execution.
    */
   @DeveloperAPI
@@ -1028,6 +1031,7 @@ class SparkContext(config: SparkConf) extends Logging {
   }
 
   /**
+   * :: DeveloperAPI ::
    * Run a job that can return approximate results.
    */
   @DeveloperAPI
@@ -1046,6 +1050,7 @@ class SparkContext(config: SparkConf) extends Logging {
   }
 
   /**
+   *
    * Submit a job for execution and return a FutureJob holding the result.
    */
   @Experimental

core/src/main/scala/org/apache/spark/SparkEnv.scala

@@ -36,6 +36,7 @@ import org.apache.spark.storage._
 import org.apache.spark.util.{AkkaUtils, Utils}
 
 /**
+ * :: DeveloperAPI ::
  * Holds all the runtime environment objects for a running Spark instance (either master or worker),
  * including the serializer, Akka actor system, block manager, map output tracker, etc. Currently
  * Spark code finds the SparkEnv through a thread-local variable, so each thread that accesses these

core/src/main/scala/org/apache/spark/TaskContext.scala

@@ -23,6 +23,7 @@ import org.apache.spark.annotations.DeveloperAPI
 import org.apache.spark.executor.TaskMetrics
 
 /**
+ * :: DeveloperAPI ::
  * Contextual information about a task which can be read or mutated during execution.
  */
 @DeveloperAPI

core/src/main/scala/org/apache/spark/TaskEndReason.scala

@@ -22,6 +22,7 @@ import org.apache.spark.executor.TaskMetrics
 import org.apache.spark.storage.BlockManagerId
 
 /**
+ * :: DeveloperAPI ::
  * Various possible reasons why a task ended. The low-level TaskScheduler is supposed to retry
  * tasks several times for "ephemeral" failures, and only report back failures that require some
  * old stages to be resubmitted, such as shuffle map fetch failures.
@@ -52,6 +53,7 @@ case class ExceptionFailure(
   extends TaskEndReason
 
 /**
+ * :: DeveloperAPI ::
  * The task finished successfully, but the result was lost from the executor's block manager before
  * it was fetched.
  */
@@ -62,13 +64,15 @@ case object TaskResultLost extends TaskEndReason
 case object TaskKilled extends TaskEndReason
 
 /**
+ * :: DeveloperAPI ::
  * The task failed because the executor that it was running on was lost. This may happen because
  * the task crashed the JVM.
  */
 @DeveloperAPI
 case object ExecutorLostFailure extends TaskEndReason
 
 /**
+ * :: DeveloperAPI ::
  * We don't know why the task ended -- for example, because of a ClassNotFound exception when
  * deserializing the task result.
  */

core/src/main/scala/org/apache/spark/broadcast/BroadcastFactory.scala

@@ -22,7 +22,8 @@ import org.apache.spark.SparkConf
 import org.apache.spark.annotations.DeveloperAPI
 
 /**
- * An interface for all the broadcast implementations in Spark (to allow 
+ * :: DeveloperAPI ::
+ * An interface for all the broadcast implementations in Spark (to allow
  * multiple broadcast implementations). SparkContext uses a user-specified
  * BroadcastFactory implementation to instantiate a particular broadcast for the
  * entire Spark job.

core/src/main/scala/org/apache/spark/executor/TaskMetrics.scala

@@ -21,6 +21,7 @@ import org.apache.spark.annotations.DeveloperAPI
 import org.apache.spark.storage.{BlockId, BlockStatus}
 
 /**
+ * :: DeveloperAPI ::
  * Metrics tracked during the execution of a task.
  */
 @DeveloperAPI
@@ -88,6 +89,7 @@ private[spark] object TaskMetrics {
 
 
 /**
+ * :: DeveloperAPI ::
  * Metrics pertaining to shuffle data read in a given task.
  */
 @DeveloperAPI
@@ -126,6 +128,7 @@ class ShuffleReadMetrics extends Serializable {
 }
 
 /**
+ * :: DeveloperAPI ::
  * Metrics pertaining to shuffle data written in a given task.
  */
 @DeveloperAPI