Add a suppression for a known V8 leak.

tools/valgrind/memcheck/suppressions.txt

 # There are three kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or 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 (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 1149 matching lines @@
 {
    bug_21010a
    Memcheck:Value4
    fun:_ZN2v88internal10PagedSpace10FindObjectEPh
 }
 {
    bug_21010b
    Memcheck:Value4
    fun:_ZN2v88internal18HeapObjectIterator17HasNextInNextPageEv
 }
+{
+  bug_22021
+  fun:malloc
+  fun:_ZN3WTF10fastMallocEj
+  fun:_ZN7WebCore19V8EventListenerList3addEPNS_15V8EventListenerE
+  fun:_ZN7WebCore19V8EventListenerList19findOrCreateWrapperINS_21V8ObjectEventListenerEEEN3WTF10PassRefPtrINS_15V8EventListenerEEEPNS_5FrameEN2v85LocalINS9_5ValueEEEb
+  fun:_ZN7WebCore12V8DOMWrapper16getEventListenerEPNS_4NodeEN2v85LocalINS3_5ValueEEEbb
+  fun:_ZN7WebCore15ElementInternal17onclickAttrSetterEN2v85LocalINS1_6StringEEENS2_INS1_5ValueEEERKNS1_12AccessorInfoE
+  fun:_ZN2v88internal21StoreCallbackPropertyENS0_9ArgumentsE
+}