Use SkSTArenaAlloc to manage SkCoverageDeltaMask's stack memory

This way, we could have more stack memory on Google3: if each of the
two branche has 12K stack memory, Google3 would believe that it needs 24K
stack memory; but using SkSTArenaAlloc, we could use 12K stack memory to
handle those two branches.

Bug: skia:
Change-Id: Ie9234226cd4ba93b5be2ebeb95ab771031354f97
Reviewed-on: https://skia-review.googlesource.com/42101
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/core/SkBlitter.cpp b/src/core/SkBlitter.cpp
index a1a1db6ce5..618eed5871 100644
--- a/src/core/SkBlitter.cpp
+++ b/src/core/SkBlitter.cpp
@@ -98,12 +98,13 @@ void SkBlitter::blitCoverageDeltas(SkCoverageDeltaList* deltas, const SkIRect& c
             continue;
         }
 
-        // If there are too many deltas, sorting will be slow. Using a mask will be much faster.
+        // If there are too many deltas, sorting will be slow. Using a mask is much faster.
         // This is such an important optimization that will bring ~2x speedup for benches like
         // path_fill_small_long_line and path_stroke_small_sawtooth.
         if (canUseMask && !deltas->sorted(y) && deltas->count(y) << 3 >= clip.width()) {
             SkIRect rowIR = SkIRect::MakeLTRB(clip.fLeft, y, clip.fRight, y + 1);
-            SkCoverageDeltaMask mask(rowIR);
+            SkSTArenaAlloc<SkCoverageDeltaMask::MAX_SIZE> alloc;
+            SkCoverageDeltaMask mask(&alloc, rowIR);
             for(int i = 0; i < deltas->count(y); ++i) {
                 const SkCoverageDelta& delta = deltas->getDelta(y, i);
                 mask.addDelta(delta.fX, y, delta.fDelta);