valgrind: Widen a suppression.

valgrind: Widen a suppression.

The Mac valgrind bot started reporting the following after
https://codereview.chromium.org/918533005/ landed:

UninitCondition
Conditional jump or move depends on uninitialised value(s)
x_zone_size
find_registered_purgeable_zone
malloc_make_nonpurgeable
imageio_make_nonpurgeable
cache_get_and_retain
CGImageReadSessionGetCachedImageBlockData
copyImageBlockSetPNG
ImageProviderCopyImageBlockSetCallback
img_blocks_create
img_blocks_extent
img_data_lock
CGSImageDataLock
ripc_AcquireImage
ripc_DrawImage
CGContextDrawImage
__-[NSImageRep drawInRect:fromRect:operation:fraction:respectFlipped:hints:]_block_invoke_1
-[NSImageRep drawInRect:fromRect:operation:fraction:respectFlipped:hints:]
__-[NSImage drawInRect:fromRect:operation:fraction:respectFlipped:hints:]_block_invoke_1
-[NSImage _usingBestRepresentationForRect:context:hints:body:]
-[NSImage drawInRect:fromRect:operation:fraction:respectFlipped:hints:]
-[NSImage hitTestRect:withImageDestinationRect:context:hints:flipped:]
ui::ThreePartImage::HitTestImage(CGPoint, NSImage*, CGRect) const
ui::ThreePartImage::HitTest(CGPoint, CGRect) const
ui::test::ThreePartImageTest_HitTest_Test::TestBody()

I can't see anything wrong, and a very similar stack is already suppressed,
so just suppress the report.

BUG=453996, 173779
TBR=andresantoso@chromium.org

Committed: https://crrev.com/99ed184ac0f7faee6b9875cdbfe2d33b7a966ffd
Cr-Commit-Position: refs/heads/master@{#316313}

[Nico, 2015-02-13 22:44:45]

The CQ bit was checked by thakis@chromium.org

[commit-bot: I haz the power, 2015-02-13 22:46:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/927733002/1

[Andre, 2015-02-13 23:02:23]

LGTM

[commit-bot: I haz the power, 2015-02-13 23:06:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-13 23:07:26]

Patchset 1 (id:??) landed as
https://crrev.com/99ed184ac0f7faee6b9875cdbfe2d33b7a966ffd
Cr-Commit-Position: refs/heads/master@{#316313}