Picture Recording: fix the performance bottleneck in SkDeferredCanvas::isFullFrame

src/utils/SkDeferredCanvas.cpp

Index: src/utils/SkDeferredCanvas.cpp
diff --git a/src/utils/SkDeferredCanvas.cpp b/src/utils/SkDeferredCanvas.cpp
index b46e92a4a09690d60da94d95a634aad43b799f7d..ac78751d142dd39a9db1d8de3ee0637b9778f525 100644
--- a/src/utils/SkDeferredCanvas.cpp
+++ b/src/utils/SkDeferredCanvas.cpp
@@ -526,6 +526,8 @@ SkDeferredCanvas::SkDeferredCanvas(SkDeferredDevice* device) : SkCanvas (device)
 void SkDeferredCanvas::init() {
     fBitmapSizeThreshold = kDeferredCanvasBitmapSizeThreshold;
     fDeferredDrawing = true; // On by default
+    fCanvasSizeChanged = true;

[reed1, 2014/09/11 15:38:13]

nit: often in skia we name this sort of boolean "Dirty" -- meaning the cache
value field it refers to is dirty and needs to be recomputed.

[yunchao, 2014/09/12 10:13:28]

Done.

+    fCanvasSize.setEmpty();

[reed1, 2014/09/11 15:38:13]

nit: may be clear to name this fCachedCanvasSize, so we don't ever think it
could be different from the computed size.

[yunchao, 2014/09/12 10:13:28]

Done.

 }
 
 void SkDeferredCanvas::setMaxRecordingStorage(size_t maxStorage) {
@@ -589,6 +591,14 @@ bool SkDeferredCanvas::isFreshFrame() const {
     return this->getDeferredDevice()->isFreshFrame();
 }
 
+SkISize SkDeferredCanvas::getCanvasSize() {
+    if (fCanvasSizeChanged) {
+        fCanvasSize = this->getBaseLayerSize();
+        fCanvasSizeChanged = false;
+    }
+    return fCanvasSize;
+}
+
 bool SkDeferredCanvas::hasPendingCommands() const {
     return this->getDeferredDevice()->hasPendingCommands();
 }
@@ -609,6 +619,7 @@ SkSurface* SkDeferredCanvas::setSurface(SkSurface* surface) {
     // all pending commands, which can help to seamlessly recover from
     // a lost accelerated graphics context.
     deferredDevice->setSurface(surface);
+    fCanvasSizeChanged = true;
     return surface;
 }
 
@@ -630,9 +641,9 @@ SkImage* SkDeferredCanvas::newImageSnapshot() {
 }
 
 bool SkDeferredCanvas::isFullFrame(const SkRect* rect,
-                                   const SkPaint* paint) const {
+                                   const SkPaint* paint) {
     SkCanvas* canvas = this->drawingCanvas();
-    SkISize canvasSize = this->getDeviceSize();
+    SkISize canvasSize = this->getCanvasSize();
     if (rect) {
         if (!canvas->getTotalMatrix().rectStaysRect()) {
             return false; // conservative