Cleanup: Remove unneeded browser_thread.h includes in contents.

android_webview/browser/aw_browser_main_parts.h

Index: android_webview/browser/aw_browser_main_parts.h
===================================================================
--- android_webview/browser/aw_browser_main_parts.h	(revision 174830)
+++ android_webview/browser/aw_browser_main_parts.h	(working copy)
@@ -5,8 +5,12 @@
 #ifndef ANDROID_WEBVIEW_BROWSER_AW_BROWSER_MAIN_PARTS_H_
 #define ANDROID_WEBVIEW_BROWSER_AW_BROWSER_MAIN_PARTS_H_
 
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "content/public/browser/browser_main_parts.h"
 
+class MessageLoop;
+
 namespace android_webview {
 
 // TODO(joth): Remove this method when when http://crbug.com/161864 is closed.
@@ -16,7 +20,7 @@
 
 class AwBrowserMainParts : public content::BrowserMainParts {
  public:
-  AwBrowserMainParts(AwBrowserContext* browser_context);
+  explicit AwBrowserMainParts(AwBrowserContext* browser_context);
   virtual ~AwBrowserMainParts();
 
   // Overriding methods from content::BrowserMainParts.