Bump CSSFilterEffects pixel test revision number to force rebaseline

This is a follow on to: https://codereview.chromium.org/2559213002/ (Add suppression for GPU Pixel test in preparation for Skia CL)

The Skia CL https://skia-review.googlesource.com/c/5747/ (Add antialiasing to SkDropShadowImageFilter's shadow draw) finally rolled into Chrome at 437566 on 12/9/2016.

BUG=672527
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2573803002
Cr-Commit-Position: refs/heads/master@{#439472}

content/test/gpu/gpu_tests/pixel_test_pages.py

@@ -317,12 +317,12 @@ def MacSpecificPages(base_name):
       'filter_effects.html',
       base_name + '_CSSFilterEffects',
       test_rect=[0, 0, 300, 300],
-      revision=3),
+      revision=4),
     PixelTestPage(
       'filter_effects.html',
       base_name + '_CSSFilterEffects_NoOverlays',
       test_rect=[0, 0, 300, 300],
-      revision=3,
+      revision=4,
       tolerance=10,
       browser_args=['--disable-mac-overlays']),
   ]