Revert of Hook up gin platform to blink, and explicitly manage the main thread isolate

Source/web/WebKit.cpp

Index: Source/web/WebKit.cpp
diff --git a/Source/web/WebKit.cpp b/Source/web/WebKit.cpp
index 47d9dbeb441b202e573731c05b4a9292683436ec..754c02d3b4a8a5ec003bdbcd31814a0add333528 100644
--- a/Source/web/WebKit.cpp
+++ b/Source/web/WebKit.cpp
@@ -42,7 +42,6 @@
 #include "core/page/Page.h"
 #include "core/frame/Settings.h"
 #include "core/workers/WorkerGlobalScopeProxy.h"
-#include "gin/public/v8_platform.h"
 #include "platform/LayoutTestSupport.h"
 #include "platform/Logging.h"
 #include "platform/graphics/ImageDecodingStore.h"
@@ -105,9 +104,7 @@
 {
     initializeWithoutV8(platform);
 
-    v8::V8::InitializePlatform(gin::V8Platform::Get());
-    v8::Isolate* isolate = v8::Isolate::New();
-    isolate->Enter();
+    v8::Isolate* isolate = v8::Isolate::GetCurrent();
     WebCore::V8Initializer::initializeMainThreadIfNeeded(isolate);
     v8::V8::SetEntropySource(&generateEntropy);
     v8::V8::SetArrayBufferAllocator(WebCore::v8ArrayBufferAllocator());
@@ -208,11 +205,9 @@
 
     ASSERT(s_isolateInterruptor);
     WebCore::ThreadState::current()->removeInterruptor(s_isolateInterruptor);
-    v8::Isolate* isolate = WebCore::V8PerIsolateData::mainThreadIsolate();
-
-    WebCore::V8PerIsolateData::dispose(isolate);
-    isolate->Exit();
-    isolate->Dispose();
+
+    WebCore::V8PerIsolateData::dispose(WebCore::V8PerIsolateData::mainThreadIsolate());
+    v8::V8::Dispose();
 
     shutdownWithoutV8();
 }