Add a Mac Valgrind suppression for an invalid free deep in the NIB loading procedure.

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 # running overnight and removing outdated bugs/suppressions.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 147 matching lines @@
 {
    # Also filed with Apple as rdar://7255382
    bug_20459b
    Memcheck:Leak
    fun:malloc_zone_malloc
    fun:_CFRuntimeCreateInstance
    fun:__CFArrayInit
    fun:CFArrayCreateMutableCopy
    fun:_ZN8Security12KeychainCore5Trust8evaluateEv
 }
+{
+   bug_32564
+   Memcheck:Free
+   fun:free
+   fun:_cache_free_block
+   fun:_cache_collect_free
+   fun:_cache_fill
+   fun:_cache_addForwardEntry
+   fun:class_respondsToSelector
+   fun:-[NSNibOutletConnector establishConnection]
+   fun:-[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:]
+   fun:loadNib
+   fun:+[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:]
+   fun:+[NSBundle(NSNibLoading) loadNibFile:externalNameTable:withZone:]
+   fun:-[NSWindowController loadWindow]
+   fun:-[NSWindowController window]
+   fun:_ZN12_GLOBAL__N_155EditSearchEngineControllerTest_ValidImageOriginals_Test8TestBodyEv
+}
 
 # 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.
 {
    # NSObject pointers in a static std::map; we do technically leak them, but
    # only on shutdown, so it's not worth fixing.
    static_theme_cache
    Memcheck:Leak
    fun:calloc
    fun:_internal_class_createInstanceFromZone
@@ skipping 492 matching lines @@
    Memcheck:Addr1
    fun:__CFBinaryPlistGetTopLevelInfo
    fun:__CFTryParseBinaryPlist
    fun:_CFPropertyListCreateFromXMLData
    fun:CFPropertyListCreateFromXMLData
    fun:_DAUnserializeWithBytes
    fun:_DASessionCallback
    fun:__CFMachPortPerform
    fun:CFRunLoopRunSpecific
 }