Add canvas blending modes behind a runtime flag

LayoutTests/fast/canvas/script-tests/canvas-blend-image.js

Index: LayoutTests/fast/canvas/script-tests/canvas-blend-image.js
diff --git a/LayoutTests/fast/canvas/script-tests/canvas-blend-image.js b/LayoutTests/fast/canvas/script-tests/canvas-blend-image.js
index 5cd0478c8b9f8e7d892e646f5fdc838c9ba48f28..e0698ce272bec2672a8b673259fe83334fdc675a 100644
--- a/LayoutTests/fast/canvas/script-tests/canvas-blend-image.js
+++ b/LayoutTests/fast/canvas/script-tests/canvas-blend-image.js
@@ -66,11 +66,10 @@ var blendModes =
 	 [[85, 0, 170, 191],[85, 85, 170, 191],[0, 43, 170, 191],[0, 0, 255, 191]]
   ],
   ['color-burn',
-	 [[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255]],
-	 [[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255]],
-	 [[128, 0, 127, 255],[128, 128, 127, 255],[0, 0, 127, 255],[0, 0, 255, 255]],
-	 [[85, 0, 170, 191],[85, 85, 170, 191],[0, 0, 170, 191],[0, 0, 255, 191]]
-
+         [[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255]],
+         [[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255],[0, 0, 255, 255]],
+         [[128, 0, 127, 255],[128, 128, 127, 255],[0, 64, 127, 255],[0, 0, 255, 255]],
+         [[85, 0, 170, 191],[85, 85, 170, 191],[0, 42, 170, 191],[0, 0, 255, 191]]
   ],
   ['hard-light',
 	 [[255, 0, 0, 255],[255, 255, 0, 255],[0, 1, 0, 255],[0, 0, 255, 255]],
@@ -173,4 +172,4 @@ function prepareTestScenario(sigma) {
   }
 
 // Run test and allow variation of results.
-prepareTestScenario(5);
+prepareTestScenario(5);