Move the <style> into the <template>

Having the CSS outside of the template makes polymer/webcomponents? insert the style without
any scoping into the final document, which can cause style leakage.

Polymer 1.x deprecated this already:
> Prior to Polymer 1.1, the recommendation was to place <style> tags inside the <dom-module> for an element (but outside the <template>). This is still supported, but is no longer recommended.
(https://www.polymer-project.org/1.0/docs/devguide/styling)

Polymer 2.0 will no longer support this according to https://www.polymer-project.org/2.0/docs/upgrade#dom-template.

See also: Polymer/polymer#3665
See also: googlearchive/polylint#132

paper-alert-dialog-icon-header.html

@@ -23,22 +23,22 @@
 -->
 <dom-module id="paper-alert-dialog-icon-header">
 
-	<style>
-		:host {
-			display: block;
-			text-align: center;
-			margin-bottom: 40px;
-			@apply(--paper-font-display1);
-		}
+	<template>
+		<style>
+			:host {
+				display: block;
+				text-align: center;
+				margin-bottom: 40px;
+				@apply(--paper-font-display1);
+			}
 
-		.icon {
-			color: var(--paper-green-500);
-			--iron-icon-width: 64px;
-			--iron-icon-height: 64px;
-		}
-	</style>
+			.icon {
+				color: var(--paper-green-500);
+				--iron-icon-width: 64px;
+				--iron-icon-height: 64px;
+			}
+		</style>
 
-	<template>
 		<iron-icon icon="[[icon]]" class="icon"></iron-icon>
 		<div><content></content></div>
 	</template>