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 cb69b4e282abee98cc95990b767fd24eae83d53d..46bd9e98f96269376b7d1081c022d7df9edc3cc1 100644
--- a/src/utils/SkDeferredCanvas.cpp
+++ b/src/utils/SkDeferredCanvas.cpp
@@ -370,6 +370,7 @@ void SkDeferredDevice::flushPendingCommands(PlaybackMode playbackMode) {
 void SkDeferredDevice::flush() {
     this->flushPendingCommands(kNormal_PlaybackMode);
     fImmediateCanvas->flush();
+    fFreshFrame = true;
 }
 
 size_t SkDeferredDevice::freeMemoryIfPossible(size_t bytesToFree) {
@@ -630,9 +631,11 @@ SkImage* SkDeferredCanvas::newImageSnapshot() {
 }
 
 bool SkDeferredCanvas::isFullFrame(const SkRect* rect,
-                                   const SkPaint* paint) const {
+                                   const SkPaint* paint) {
     SkCanvas* canvas = this->drawingCanvas();
-    SkISize canvasSize = this->getDeviceSize();
+    if (isFreshFrame()) {

[yunchao, 2014/09/05 08:43:13]

maybe I should implement a new method named isNewFrame(), and update fNewFrame
only in SkDeferredDevice::flush. Don't update it in
SkDeferredDevice::skipPendingCommands.

[reed1, 2014/09/05 13:18:33]

nit: this->isFreshFrame()

[Justin Novosad, 2014/09/05 13:54:49]

isFreshFrame is not the right condition for refreshing the cached size. In
general, caches should be invalidated by actions that affect the value that is
cached.  The only calls that could affect the device size are: setSurface(),
saveLayer, and a restore call that is associated with a saveLayer.  These
actions are completely independent of flushing.

[yunchao, 2014/09/09 08:58:00]

Done.

[yunchao, 2014/09/09 08:58:00]

Done. Added a new interface SkDeferredCanvas::canvasSizeChanged.

+        canvasSize = this->getDeviceSize();
+    }
     if (rect) {
         if (!canvas->getTotalMatrix().rectStaysRect()) {
             return false; // conservative