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

blink skips all pending commands during picture recording if it is drawing an opaque full-frame
geometry or image. This may improve performance for some edge cases. To recognize an opaque
full-frame drawing should be cheap enough. Otherwise, the overhead will offset the improvement.
Unfortunately, data from perf for content_shell on Nexus7 shows that SkDeferredCanvas::isFullFrame
is far from cheap. Table below shows that how much isFullFrame() costs in the whole render process.

benchmark                              percentage
my local benchmark(draw 1000 sprites)   4.1%
speedReading                            2.8%
FishIETank(1000 fishes)                 1.5%
GUIMark3 Bitmap                         2.0%

By contrast, real recording (SkGPipeCanvas::drawBitmapRectToRect) and real rasterization
(GrDrawTarget::drawRect) cost ~4% and ~6% in the whole render process respectively. Apparently,
SkDeferredCanvas::isFullFrame() is nontrivial.

getDeviceSize() is the main contributor to this hotspot. The change simply save the canvasSize and
reuse it among drawings if it is not a fresh frame. This change cut off ~65% (or improved ~2 times)
of isFullFrame().

telemetry smoothness canvas_tough_test didn't show obvious improvement or regression.

BUG=411166

Committed: https://skia.googlesource.com/skia/+/8e45c3777d886ba3fe239bb549d06b0693692152

R=junov@chromium.org, tomhudson@google.com, reed@google.com

Author: yunchao.he@intel.com

Review URL: https://codereview.chromium.org/545813002

1 files changed, 8 insertions, 0 deletions

diff --git a/include/utils/SkDeferredCanvas.h b/include/utils/SkDeferredCanvas.h
index 907cb91575..5f781f8859 100644
--- a/include/utils/SkDeferredCanvas.h
+++ b/include/utils/SkDeferredCanvas.h
@@ -89,6 +89,11 @@ public:
     bool isFreshFrame() const;
 
     /**
+     * Returns canvas's size.
+     */
+    SkISize getCanvasSize() const;
+
+    /**
      *  Returns true if the canvas has recorded draw commands that have
      *  not yet been played back.
      */
@@ -250,6 +255,9 @@ private:
     size_t fBitmapSizeThreshold;
     bool   fDeferredDrawing;
 
+    mutable SkISize fCachedCanvasSize;
+    mutable bool    fCachedCanvasSizeDirty;
+
     friend class SkDeferredCanvasTester; // for unit testing
     typedef SkCanvas INHERITED;
 };