[SP] Allocate an SkPictureRecorder only once per GraphicsContext instantiation

Source/platform/graphics/GraphicsContext.cpp

Index: Source/platform/graphics/GraphicsContext.cpp
diff --git a/Source/platform/graphics/GraphicsContext.cpp b/Source/platform/graphics/GraphicsContext.cpp
index 62c278281ef1aeef0be5148bd72acb027d9d80ff..8ded7947e1ac8e0aa85a66e15093152e612efd37 100644
--- a/Source/platform/graphics/GraphicsContext.cpp
+++ b/Source/platform/graphics/GraphicsContext.cpp
@@ -56,6 +56,8 @@ class GraphicsContext::RecordingState {
 public:
     static PassOwnPtr<RecordingState> Create(SkCanvas* canvas, const SkMatrix& matrix)
     {
+        // Slimmming Paint uses m_pictureRecorder on GraphicsContext instead.
+        ASSERT(!RuntimeEnabledFeatures::slimmingPaintEnabled());
         return adoptPtr(new RecordingState(canvas, matrix));
     }
 
@@ -76,7 +78,10 @@ private:
 
 GraphicsContext::GraphicsContext(DisplayItemList* displayItemList, DisabledMode disableContextOrPainting)
     : GraphicsContext(nullptr, displayItemList, disableContextOrPainting)
-{ }
+{
+    // TODO(chrishtr): switch the type of the parameter to DisplayItemList&.
+    ASSERT(displayItemList);
+}
 
 PassOwnPtr<GraphicsContext> GraphicsContext::deprecatedCreateWithCanvas(SkCanvas* canvas, DisabledMode disableContextOrPainting)
 {
@@ -85,6 +90,7 @@ PassOwnPtr<GraphicsContext> GraphicsContext::deprecatedCreateWithCanvas(SkCanvas
 
 GraphicsContext::GraphicsContext(SkCanvas* canvas, DisplayItemList* displayItemList, DisabledMode disableContextOrPainting)
     : m_canvas(canvas)
+    , m_originalCanvas(canvas)
     , m_displayItemList(displayItemList)
     , m_clipRecorderStack(0)
     , m_paintStateStack()
@@ -472,6 +478,11 @@ void GraphicsContext::beginRecording(const FloatRect& bounds, uint32_t recordFla
     if (contextDisabled())
         return;
 
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+        m_canvas = m_pictureRecorder.beginRecording(bounds, 0, recordFlags);
+        return;
+    }
+
     m_recordingStateStack.append(
         RecordingState::Create(m_canvas, getTotalMatrix()));
     m_canvas = m_recordingStateStack.last()->recorder().beginRecording(bounds, 0, recordFlags);
@@ -482,6 +493,13 @@ PassRefPtr<const SkPicture> GraphicsContext::endRecording()
     if (contextDisabled())
         return nullptr;
 
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+        RefPtr<const SkPicture> picture = adoptRef(m_pictureRecorder.endRecordingAsPicture());
+        m_canvas = m_originalCanvas;
+        ASSERT(picture);
+        return picture.release();
+    }
+
     ASSERT(!m_recordingStateStack.isEmpty());
     RecordingState* recording = m_recordingStateStack.last().get();
     RefPtr<const SkPicture> picture = adoptRef(recording->recorder().endRecordingAsPicture());
@@ -495,6 +513,9 @@ PassRefPtr<const SkPicture> GraphicsContext::endRecording()
 
 bool GraphicsContext::isRecording() const
 {
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled())
+        return m_canvas != m_originalCanvas;
+
     return !m_recordingStateStack.isEmpty();
 }