Expose platform thread id on WebThread

Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "platform/graphics/RecordingImageBufferSurface.h"
 
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/ImageBuffer.h"
@@ skipping 224 matching lines @@
 
         virtual void postTask(Task* task)
         {
             EXPECT_EQ((Task*)0, m_task);
             m_task = task;
         }
 
         virtual void postDelayedTask(Task*, long long delayMs) OVERRIDE { ASSERT_NOT_REACHED(); };
 
         virtual bool isCurrentThread() const OVERRIDE { return true; }
+        virtual PlatformThreadId threadId() const OVERRIDE
+        {
+            ASSERT_NOT_REACHED();
+            return 0;
+        }
 
         virtual void addTaskObserver(TaskObserver* taskObserver) OVERRIDE
         {
             EXPECT_EQ((TaskObserver*)0, m_taskObserver);
             m_taskObserver = taskObserver;
         }
 
         virtual void removeTaskObserver(TaskObserver* taskObserver) OVERRIDE
         {
             EXPECT_EQ(m_taskObserver, taskObserver);
@@ skipping 92 matching lines @@
 }
 
 DEFINE_TEST_TASK_WRAPPER_CLASS(testClearRect)
 TEST_F(RecordingImageBufferSurfaceTest, testClearRect)
 {
     CALL_TEST_TASK_WRAPPER(testClearRect);
     expectDisplayListEnabled(true);
 }
 
 } // namespace