Remove unneeded suppression for reverted unified Gesture Recognizer.

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 # running overnight and removing outdated bugs/suppressions.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 6403 matching lines @@
 {
    bug_371860
    Memcheck:Leak
    fun:_Znw*
    ...
    fun:_ZN8feedback20FeedbackUploaderTestC1Ev
    fun:_ZN8feedback*FeedbackUploaderTest*
    fun:_ZN7testing8internal15TestFactoryImplIN8feedback*
 }
 {
-   bug_372143
-   Memcheck:Leak
-   fun:_Znw*
-   ...
-   fun:_ZN2ui12_GLOBAL__N_121CreateGestureProviderEPNS_25GestureProviderAuraClientE
-   fun:_ZN2ui21GestureRecognizerImpl29GetGestureProviderForConsumerEPNS_15GestureConsumerE
-   fun:_ZN2ui21GestureRecognizerImpl27ProcessTouchEventForGestureERKNS_10TouchEventENS_11EventResultEPNS_15GestureConsumerE
-   fun:_ZN4aura21WindowEventDispatcher17PostDispatchEventEPN2ui11EventTargetERKNS1_5EventE
-   fun:_ZN2ui23EventDispatcherDelegate13DispatchEventEPNS_11EventTargetEPNS_5EventE
-   fun:_ZN2ui14EventProcessor17OnEventFromSourceEPNS_5EventE
-   fun:_ZN4aura4test12AuraTestBase34DispatchEventUsingWindowDispatcherEPN2ui5EventE
-}
-{
    bug_372226
    Memcheck:Uninitialized
    ...
    fun:_ZN7WebCore13PinchViewport5resetEv
    ...
    fun:_ZN7WebCore13PinchViewportC1ERNS_9FrameHostE
    ...
    fun:_ZN7WebCore9FrameHostC1ERNS_4PageE
 }
 {
    bug_371974
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN4base8internal20PostTaskAndReplyImpl16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvEEESA_
    fun:_ZN4base10TaskRunner16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvEEES9_
    fun:_ZN4base26PostTaskAndReplyWithResultIbbEEbPNS_10TaskRunnerERKN15tracked_objects8LocationERKNS_8CallbackIFT_vEEERKNS7_IFvT0_EEE
    fun:_ZN4base19ImportantFileWriter8WriteNowERKSs
 }