Fix memory leak introduced by r22043.

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 # running overnight and removing outdated bugs/suppressions.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 936 matching lines @@
    bug_17996
    Memcheck:Leak
    ...
    fun:_ZN7WebCore10StringImplnwEj
    fun:_ZN3WTF9HashTableIPN7WebCore10StringImplES3_NS_17IdentityExtractorIS3_EENS1_10StringHashENS_10HashTraitsIS3_EES8_E18addPassingHashCodeIPKcSC_NS_24HashSetTranslatorAdapterIS3_S8_SC_NS1_17CStringTranslatorEEEEESt4pairINS_17HashTableIteratorIS3_S3_S5_S6_S8_S8_EEbERKT_RKT0_
    fun:_ZN3WTF7HashSetIPN7WebCore10StringImplENS1_10StringHashENS_10HashTraitsIS3_EEE3addIPKcNS1_17CStringTranslatorEEESt4pairINS_24HashTableIteratorAdapterINS_9HashTableIS3_S3_NS_17IdentityExtractorIS3_EES4_S6_S6_EES3_EEbERKT_
    fun:_ZN7WebCore12AtomicString3addEPKc
    fun:_ZN7WebCore12AtomicStringC1EPKc
    fun:_ZN7WebCore8SVGNames4initEv
 }
-{
-  crbug_18070
-  Memcheck:Leak
-  ...
-  fun:_ZN7Version20GetVersionFromStringERKSs
-  fun:_ZN17ExtensionsService24OnExternalExtensionFoundERKSsS1_RK8FilePathN9Extension8LocationE
-  fun:_ZN14RunnableMethodI17ExtensionsServiceMS0_FvRKSsS2_RK8FilePathN9Extension8LocationEE6Tuple4ISsSsS3_S7_EE3RunEv
-  fun:_ZN11MessageLoop7RunTaskEP4Task
-  fun:_ZN11MessageLoop21DeferOrRunPendingTaskERKNS_11PendingTaskE
-  fun:_ZN11MessageLoop6DoWorkEv
-  fun:_ZN4base18MessagePumpDefault3RunEPNS_11MessagePump8DelegateE
-  fun:_ZN11MessageLoop11RunInternalEv
-  fun:_ZN11MessageLoop10RunHandlerEv
-  fun:_ZN11MessageLoop13RunAllPendingEv
-  fun:_ZN46ExtensionsServiceTest_ExternalInstallPref_Test8TestBodyEv
-  fun:_ZN7testing4Test3RunEv
-  fun:_ZN7testing8internal12TestInfoImpl3RunEv
-  fun:_ZN7testing8internal12TestInfoImpl7RunTestEPNS_8TestInfoE
-  fun:_ZN7testing8TestCase3RunEv
-  fun:_ZN7testing8TestCase11RunTestCaseEPS0_
-  fun:_ZN7testing8internal12UnitTestImpl11RunAllTestsEv
-  fun:_ZN7testing8UnitTest3RunEv
-}