[MemSheriff] Widen existing suppression.

tools/valgrind/memcheck/suppressions_mac.txt

 # There are three kinds of suppressions in this file:
 # 1. Third party stuff we have no control over.
 #
 # 2. Intentional unit test errors, stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing.
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system.
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 94 matching lines @@
    bug_257276
    Memcheck:Leak
    ...
    fun:ripc_DrawPath
    fun:CGContextDrawPath
 }
 {
    bug_257276_b
    Memcheck:Leak
    fun:malloc_zone_malloc
-   fun:_CFRuntimeCreateInstance
-   fun:CFNumberCreate
-   fun:get_colorspace
-   fun:initImagePng
-   fun:_CGImagePluginInitPNG
-   fun:makeImagePlus
-   fun:CGImageSourceCreateImageAtIndex
-   fun:CGImageCreateWithPNGDataProvider
+   ...
    fun:setCursorFromBundle
    fun:CoreCursorSet
    fun:-[NSCursor set]
 }
 
 # 2. Intentional unit test errors, stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing.
 {
    # Mac Sandbox test cases are registered in a global map.  This code is only
    # used in the unit test binary.
@@ skipping 2319 matching lines @@
    fun:-[NSBundle _initInfoDictionary]
    fun:+[NSBundle mainBundle]
    fun:_ZN4base3mac11OuterBundleEv
    fun:_ZN4base3mac12_GLOBAL__N_118UncachedAmIBundledEv
    fun:_ZN4base3mac10AmIBundledEv
    fun:_ZN7content25TestWebKitPlatformSupportC2Ev
    fun:_ZN7content25TestWebKitPlatformSupportC1Ev
    fun:_ZN7content17UnitTestTestSuiteC2EPN4base9TestSuiteE
    fun:_ZN7content17UnitTestTestSuiteC1EPN4base9TestSuiteE
 }