Fix leaks in exensions_unittests after enabling Oilpan

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 # running overnight and removing outdated bugs/suppressions.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 3387 matching lines @@
    ...
    fun:_ZN7GrGLGpu6CreateElRK16GrContextOptionsP9GrContext
    fun:_ZN5GrGpu6CreateE9GrBackendlRK16GrContextOptionsP9GrContext
    fun:_ZN9GrContext4initE9GrBackendlRK16GrContextOptions
    fun:_ZN9GrContext6CreateE9GrBackendlRK16GrContextOptions
    fun:_ZN9GrContext6CreateE9GrBackendl
    ...
    fun:_ZN2cc10GLRenderer18DrawRenderPassQuadEPNS_14DirectRenderer12DrawingFrameEPKNS_18RenderPassDrawQuadEPKN3gfx5QuadFE
    fun:_ZN2cc10GLRenderer10DoDrawQuadEPNS_14DirectRenderer12DrawingFrameEPKNS_8DrawQuadEPKN3gfx5QuadFE
 }
-{
-   bug_581092_a
-   Memcheck:Leak
-   ...
-   fun:_ZN5blink15ContextFeatures13defaultSwitchEv
-   fun:_ZN5blink8DocumentC2ERKNS_12DocumentInitEh
-   fun:_ZN5blink12HTMLDocumentC1ERKNS_12DocumentInitEh
-   fun:_ZN5blink12HTMLDocument6createERKNS_12DocumentInitE
-   fun:_ZN5blink17DOMImplementation14createDocumentERKN3WTF6StringERKNS_12DocumentInitEb
-   fun:_ZN5blink14LocalDOMWindow14createDocumentERKN3WTF6StringERKNS_12DocumentInitEb
-   fun:_ZN5blink14LocalDOMWindow18installNewDocumentERKN3WTF6StringERKNS_12DocumentInitEb
-   fun:_ZN5blink14DocumentLoader15createWriterForEPKNS_*
-}
-{
-   bug_581092_b
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN5blink26RefCountedGarbageCollectedINS_15StyleFilterDataEE13makeKeepAliveEv
-   fun:_ZN5blink26RefCountedGarbageCollectedINS_15StyleFilterDataEE3refEv
-   ...
-   fun:_ZN5blink7DataRefINS_15StyleFilterDataEE4initEv
-   ...
-   fun:_ZN5blink13ComputedStyle6createEv
-   fun:_ZN5blink13StyleResolver16styleForDocumentERNS_8DocumentE
-   fun:_ZN5blink8Document6attachERKNS_4Node13AttachContextE
-   fun:_ZN5blink14LocalDOMWindow18installNewDocumentERKN3WTF6StringERKNS_12DocumentInitEb
-   fun:_ZN5blink14DocumentLoader15createWriterForEPKNS_*
-}