Modifications to DisplayList for better Slimming Paint

Source/platform/graphics/GraphicsContext.h

Index: Source/platform/graphics/GraphicsContext.h
diff --git a/Source/platform/graphics/GraphicsContext.h b/Source/platform/graphics/GraphicsContext.h
index 7257345af0877984fcc9a48a932d04b526926614..a237fcfa11d14c91d6a78f54800bee5ae3db5581 100644
--- a/Source/platform/graphics/GraphicsContext.h
+++ b/Source/platform/graphics/GraphicsContext.h
@@ -310,10 +310,15 @@ public:
     void clip(const FloatRect& rect) { clipRect(rect); }
     void clipRoundedRect(const RoundedRect&, SkRegion::Op = SkRegion::kIntersect_Op);
     void clipOut(const IntRect& rect) { clipRect(rect, NotAntiAliased, SkRegion::kDifference_Op); }
+    void clipOut(const Path&);
     void clipOutRoundedRect(const RoundedRect&);
     void clipPath(const Path&, WindRule = RULE_EVENODD);
     void clipConvexPolygon(size_t numPoints, const FloatPoint*, bool antialias = true);
     void clipRect(const SkRect&, AntiAliasingMode = NotAntiAliased, SkRegion::Op = SkRegion::kIntersect_Op);
+    // This clip function is used only by <canvas> code. It allows
+    // implementations to handle clipping on the canvas differently since
+    // the discipline is different.
+    void canvasClip(const Path&, WindRule = RULE_EVENODD);
 
     void drawText(const Font&, const TextRunPaintInfo&, const FloatPoint&);
     void drawEmphasisMarks(const Font&, const TextRunPaintInfo&, const AtomicString& mark, const FloatPoint&);
@@ -335,9 +340,10 @@ public:
     void endCull();
 
     // Instead of being dispatched to the active canvas, draw commands following beginRecording()
-    // are stored in a display list that can be replayed at a later time.
-    void beginRecording(const FloatRect& bounds);
-    PassRefPtr<DisplayList> endRecording();
+    // are stored in a display list that can be replayed at a later time. Pass in the bounding
+    // rectangle for the content in the list.
+    PassRefPtr<DisplayList> beginRecording(const FloatRect&, uint32_t = 0);
+    void endRecording();

[chrishtr, 2014/09/05 01:15:34]

after endRecording() is called, the GraphicsContext promises to treat the
display list as a const object right? That deserves a comment.
How about adding a field on DisplayList such as displayList.lock() to enforce
that? Hmm..

[Stephen Chennney, 2014/09/05 13:50:50]

We can just assert that there is no picture before we start recording with the
list. If a picture exists, it's locked. I would put that in the follow on patch.

 
     bool hasShadow() const;
     void setShadow(const FloatSize& offset, float blur, const Color&,
@@ -364,12 +370,6 @@ public:
     typedef unsigned Edges;
     void drawInnerShadow(const RoundedRect&, const Color& shadowColor, const IntSize shadowOffset, int shadowBlur, int shadowSpread, Edges clippedEdges = NoEdge);
 
-    // This clip function is used only by <canvas> code. It allows
-    // implementations to handle clipping on the canvas differently since
-    // the discipline is different.
-    void canvasClip(const Path&, WindRule = RULE_EVENODD);
-    void clipOut(const Path&);
-
     // ---------- Transformation methods -----------------
     // Note that the getCTM method returns only the current transform from Blink's perspective,
     // which is not the final transform used to place content on screen. It cannot be relied upon
@@ -448,7 +448,6 @@ private:
     void drawFocusRingPath(const SkPath&, const Color&, int width);
     void drawFocusRingRect(const SkRect&, const Color&, int width);
 
-
     // SkCanvas wrappers.
     void clipPath(const SkPath&, AntiAliasingMode = NotAntiAliased, SkRegion::Op = SkRegion::kIntersect_Op);
     void clipRRect(const SkRRect&, AntiAliasingMode = NotAntiAliased, SkRegion::Op = SkRegion::kIntersect_Op);