Fix cause of uninitialized memory read in ExtensionService unit_tests

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 # running overnight and removing outdated bugs/suppressions.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 5251 matching lines @@
    bug_106402
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN2pp25CompletionCallbackFactoryIN5ppapi5proxy20PPB_Graphics2D_ProxyENS2_26ProxyNonThreadSafeRefCountEE17NewCallbackHelperINS5_11Dispatcher1IMS3_FviRKNS1_12HostResourceEES8_EEEENS_18CompletionCallbackERKT_
    fun:_ZN2pp25CompletionCallbackFactoryIN5ppapi5proxy20PPB_Graphics2D_ProxyENS2_26ProxyNonThreadSafeRefCountEE11NewCallbackIMS3_FviRKNS1_12HostResourceEES7_EENS_18CompletionCallbackET_RKT0_
    fun:_ZN2pp25CompletionCallbackFactoryIN5ppapi5proxy20PPB_Graphics2D_ProxyENS2_26ProxyNonThreadSafeRefCountEE19NewOptionalCallbackIMS3_FviRKNS1_12HostResourceEES7_EENS_18CompletionCallbackET_RKT0_
    fun:_ZN5ppapi5proxy38EnterHostFromHostResourceForceCallbackINS_5thunk18PPB_Graphics2D_APIEEC1IN2pp25CompletionCallbackFactoryINS0_20PPB_Graphics2D_ProxyENS0_26ProxyNonThreadSafeRefCountEEEMS8_FviRKNS_12HostResourceEESB_EESD_RT_T0_RKT1_
    fun:_ZN5ppapi5proxy20PPB_Graphics2D_Proxy14OnHostMsgFlushERKNS_12HostResourceE
 }
 {
-   bug_106549
-   Memcheck:Uninitialized
-   fun:_ZN16ExtensionService24ProcessExtensionSyncDataERK17ExtensionSyncDataRNS_10SyncBundleE
-   fun:_ZN16ExtensionService18ProcessSyncChangesERKN15tracked_objects8LocationERKSt6vectorI10SyncChangeSaIS5_EE
-}
-{
    bug_106552
    Memcheck:Uninitialized
    ...
    fun:_ZN25JSONStringValueSerializer17SerializeInternalERKN4base5ValueEb
    fun:_ZN25JSONStringValueSerializer9SerializeERKN4base5ValueE
    fun:_ZN13JsonPrefStore13SerializeDataEPSs
    fun:_ZN19ImportantFileWriter16DoScheduledWriteEv
    fun:_ZN13JsonPrefStore18CommitPendingWriteEv
    fun:_ZN13JsonPrefStoreD0Ev
    fun:_ZNK4base10RefCountedI9PrefStoreE7ReleaseEv
@@ skipping 54 matching lines @@
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }
 {
    bug_todo_grep
    Memcheck:Leak
    fun:malloc
    obj:/bin/grep
    obj:/bin/grep
 }