Remove suppression for MessageChannel.create()

tools/valgrind/memcheck/suppressions.txt

 # There are four 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 # running overnight and removing outdated bugs/suppressions.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 6387 matching lines @@
 {
    bug_310351
    Memcheck:Leak
    ...
    fun:_ZN3WTF12PthreadStatenwEm
    fun:_ZN3WTFL35establishIdentifierForPthreadHandleERK*
    fun:_ZN3WTF13currentThreadEv
    fun:_ZN3WTF20initializeMainThreadEPFvPFvPvES0_E
 }
 {
-   bug_311229
-   Memcheck:Leak
-   fun:malloc
-   fun:_ZN3WTF10fastMallocEm
-   fun:_ZN3WTF24ThreadSafeRefCountedBasenwEm
-   fun:_ZN7WebCore18MessagePortChannel6createEPN5blink21WebMessagePortChannelE
-   fun:_ZN7WebCore18MessagePortChannel13createChannelEPNS_11MessagePortES2_
-   fun:_ZN7WebCore14MessageChannelC1EPNS_16ExecutionContextE
-   fun:_ZN7WebCore14MessageChannel6createEPNS_16ExecutionContextE
-   fun:_ZN7WebCore16V8MessageChannel17constructorCustomERKN2v820FunctionCallbackInfoINS1_5ValueEEE
-   fun:_ZN7WebCore16V8MessageChannel19constructorCallbackERKN2v820FunctionCallbackInfoINS1_5ValueEEE
-   fun:_ZN2v88internal25FunctionCallbackArguments4CallEPFvRKNS_20FunctionCallbackInfoINS_5ValueEEEE
-   fun:_ZN2v88internalL19HandleApiCallHelperILb1EEEPNS0_11MaybeObjectENS0_12_GLOBAL__N_116BuiltinArgumentsILNS0_21BuiltinExtraArgumentsE1EEEPNS0_7IsolateE
-   fun:_ZN2v88internalL34Builtin_implHandleApiCallConstructENS0_12_GLOBAL__N_116BuiltinArgumentsILNS0_21BuiltinExtraArgumentsE1EEEPNS0_7IsolateE
-   fun:_ZN2v88internalL30Builtin_HandleApiCallConstructEiPPNS0_6ObjectEPNS0_7IsolateE
-}
-{
    bug_312332
    Memcheck:Uninitialized
    ...
    fun:_ZNK7WebCore17RenderTextControl29computeIntrinsicLogicalWidthsERNS_10LayoutUnitES2_
    fun:_ZN7WebCore17RenderTextControl29computePreferredLogicalWidthsEv
    ...
    fun:_ZN7WebCore11RenderBlock6layoutEv
 }