Move GraphicsContextTest to platform/ and fix the test environment.

Source/platform/TestingPlatformSupport.cpp

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 66 matching lines @@
 
 blink::WebDiscardableMemory* TestingPlatformSupport::allocateAndLockDiscardableMemory(size_t bytes)
 {
     return !m_config.hasDiscardableMemorySupport ? 0 : new TestingDiscardableMemory(bytes);
 }
 
 void TestingPlatformSupport::cryptographicallyRandomValues(unsigned char* buffer, size_t length)
 {
 }
 
+const unsigned char* TestingPlatformSupport::getTraceCategoryEnabledFlag(const char* categoryName)
+{
+    static const unsigned char tracingIsDisabled = 0;
+    return &tracingIsDisabled;
+}
+
 } // namespace WebCore