Adding WebThread and new BlinkPlatformImpl for utility thread.

content/utility/utility_thread_impl.cc

Index: content/utility/utility_thread_impl.cc
diff --git a/content/utility/utility_thread_impl.cc b/content/utility/utility_thread_impl.cc
index 7ea1a1d409b7207dee3f47f4be13d0edfcd9e520..18d54f7bee7be732c9a3e16415d2f865fe044b1b 100644
--- a/content/utility/utility_thread_impl.cc
+++ b/content/utility/utility_thread_impl.cc
@@ -80,7 +80,7 @@ void UtilityThreadImpl::Init() {
     // we run the utility thread on separate thread. This means that if any code
     // needs WebKit initialized in the utility process, they need to have
     // another path to support single process mode.
-    blink_platform_impl_.reset(new BlinkPlatformImpl);
+    blink_platform_impl_.reset(new UtilityBlinkPlatformImpl);
     blink::initialize(blink_platform_impl_.get());
   }
   GetContentClient()->utility()->UtilityThreadStarted();