Add some more logs for diagnosing screenshot failures

shell/common/rasterizer.cc

@@ -173,6 +173,7 @@ static sk_sp<SkData> ScreenshotLayerTreeAsImage(
   auto snapshot_surface =
       CreateSnapshotSurface(surface_context, tree->frame_size());
   if (snapshot_surface == nullptr) {
+    FML_LOG(ERROR) << "Screenshot: unable to create snapshot surface";
     return nullptr;
   }
 
@@ -193,16 +194,18 @@ static sk_sp<SkData> ScreenshotLayerTreeAsImage(
   // Prepare an image from the surface, this image may potentially be on th GPU.
   auto potentially_gpu_snapshot = snapshot_surface->makeImageSnapshot();
   if (!potentially_gpu_snapshot) {
+    FML_LOG(ERROR) << "Screenshot: unable to make image screenshot";
     return nullptr;
   }
 
   // Copy the GPU image snapshot into CPU memory.
   auto cpu_snapshot = potentially_gpu_snapshot->makeRasterImage();
   if (!cpu_snapshot) {
+    FML_LOG(ERROR) << "Screenshot: unable to make raster image";
     return nullptr;
   }
 
-  // If the caller want the pixels to be compressed, there is a Skia utilitiy to
+  // If the caller want the pixels to be compressed, there is a Skia utility to
   // compress to PNG. Use that.
   if (compressed) {
     return cpu_snapshot->encodeToData();
@@ -211,6 +214,7 @@ static sk_sp<SkData> ScreenshotLayerTreeAsImage(
   // Copy it into a bitmap and return the same.
   SkPixmap pixmap;
   if (!cpu_snapshot->peekPixels(&pixmap)) {
+    FML_LOG(ERROR) << "Screenshot: unable to obtain bitmap pixels";
     return nullptr;
   }
 
@@ -222,7 +226,7 @@ Rasterizer::Screenshot Rasterizer::ScreenshotLastLayerTree(
     bool base64_encode) {
   auto layer_tree = GetLastLayerTree();
   if (layer_tree == nullptr) {
-    FML_DLOG(INFO) << "Last layer tree was null when screenshotting.";
+    FML_LOG(ERROR) << "Last layer tree was null when screenshotting.";
     return {};
   }
 
@@ -246,7 +250,7 @@ Rasterizer::Screenshot Rasterizer::ScreenshotLastLayerTree(
   }
 
   if (data == nullptr) {
-    FML_DLOG(INFO) << "Sceenshot data was null.";
+    FML_LOG(ERROR) << "Screenshot data was null.";
     return {};
   }