Fix 2D canvas drawImage handling of non-invertible transform matrices

BUG=504687

Review URL: https://codereview.chromium.org/1216523005

git-svn-id: svn://svn.chromium.org/blink/trunk@198018 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext2D.cpp

@@ -1322,7 +1322,11 @@ void CanvasRenderingContext2D::drawImageInternal(CanvasImageSource* imageSource,
         SkMatrix ctm = c->getTotalMatrix();
         SkMatrix invCtm;
         if (!ctm.invert(&invCtm)) {
-            ASSERT_NOT_REACHED(); // There is an earlier check for invertibility
+            // There is an earlier check for invertibility, but the arithmetic
+            // in AffineTransform is not exactly identical, so it is possible
+            // for SkMatrix to find the transform to be non-invertible at this stage.
+            // crbug.com/504687
+            return;
         }
         c->save();
         c->concat(invCtm);