[Slimming Paint] Paint the inspector overlay with GraphicsLayer DisplayList.

Source/web/WebGraphicsContextImpl.cpp

Index: Source/web/WebGraphicsContextImpl.cpp
diff --git a/Source/web/WebGraphicsContextImpl.cpp b/Source/web/WebGraphicsContextImpl.cpp
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index 0000000000000000000000000000000000000000..a42783600791c9b96b19af395ae21db2fc3f082a
--- /dev/null
+++ b/Source/web/WebGraphicsContextImpl.cpp
@@ -0,0 +1,46 @@
+// Copyright 2015 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 "web/WebGraphicsContextImpl.h"
+
+#include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/paint/DrawingRecorder.h"
+
+namespace blink {
+
+WebGraphicsContextImpl::WebGraphicsContextImpl(GraphicsContext& graphicsContext, DisplayItemClient client, DisplayItem::Type type)
+    : m_graphicsContext(graphicsContext)
+    , m_client(client)
+    , m_type(type)
+#ifndef NDEBUG
+    , m_hasBegunDrawing(false)
+#endif
+{
+}
+
+WebGraphicsContextImpl::~WebGraphicsContextImpl()
+{
+}
+
+WebCanvas* WebGraphicsContextImpl::beginDrawing(const WebFloatRect& bounds)
+{
+#ifndef NDEBUG
+    ASSERT(!m_hasBegunDrawing);
+    m_hasBegunDrawing = true;
+#endif
+    m_drawingRecorder = adoptPtr(new DrawingRecorder(&m_graphicsContext, m_client, m_type, bounds));
+
+    WebCanvas* canvas = m_graphicsContext.canvas();
+    ASSERT(canvas);
+    return canvas;
+}
+
+void WebGraphicsContextImpl::endDrawing()
+{
+    ASSERT(m_drawingRecorder);
+    m_drawingRecorder.clear();
+}
+
+} // namespace blink