Short circuit RenderTestRule comparison

Short circuits RenderTestRule's Bitmap comparison if Bitmap.sameAs
returns true. This comparison is signiciantly faster than the fallback
pixel-by-pixel comparison, particularly when comparing large images like
those produced by VR.

Bug: 904012
Change-Id: Ia9cdd91c91f94079d853ec28fd49fee3c3dd0905
Reviewed-on: https://chromium-review.googlesource.com/c/1334945Reviewed-by: Peter Conn <peconn@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608030}

chrome/test/android/javatests/src/org/chromium/chrome/test/util/RenderTestRule.java

@@ -340,6 +340,9 @@ public class RenderTestRule extends TestWatcher {
     private static Pair<ComparisonResult, Bitmap> compareBitmapToGolden(
             Bitmap render, Bitmap golden) {
         if (golden == null) return Pair.create(ComparisonResult.GOLDEN_NOT_FOUND, null);
+        // This comparison is much, much faster than doing a pixel-by-pixel comparison, so try this
+        // first and only fall back to the pixel comparison if it fails.
+        if (render.sameAs(golden)) return Pair.create(ComparisonResult.MATCH, null);
 
         Bitmap diff = Bitmap.createBitmap(Math.max(render.getWidth(), golden.getWidth()),
                 Math.max(render.getHeight(), golden.getHeight()), render.getConfig());