Fix image decode thrashing when drawing a very large source image to a GPU canvas

R=bsalomon@google.com

Author: junov@chromium.org

Review URL: https://codereview.chromium.org/265763005

git-svn-id: http://skia.googlecode.com/svn/trunk/src@14522 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 5 insertions, 0 deletions

diff --git a/gpu/SkGpuDevice.cpp b/gpu/SkGpuDevice.cpp
index 4af16109..60b4e7c4 100644
--- a/gpu/SkGpuDevice.cpp
+++ b/gpu/SkGpuDevice.cpp
@@ -1289,6 +1289,11 @@ void SkGpuDevice::drawTiledBitmap(const SkBitmap& bitmap,
                                   SkCanvas::DrawBitmapRectFlags flags,
                                   int tileSize,
                                   bool bicubic) {
+    // The following pixel lock is technically redundant, but it is desirable
+    // to lock outside of the tile loop to prevent redecoding the whole image
+    // at each tile in cases where 'bitmap' holds an SkDiscardablePixelRef that
+    // is larger than the limit of the discardable memory pool.
+    SkAutoLockPixels alp(bitmap);
     SkRect clippedSrcRect = SkRect::Make(clippedSrcIRect);
 
     int nx = bitmap.width() / tileSize;