Fix leak in pnacl translation cache and remove check suppressions

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 # running overnight and removing outdated bugs/suppressions.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 7337 matching lines @@
 }
 {
    bug_245952b
    Memcheck:Param
    pwrite64(buf)
    obj:/lib/x86_64-linux-gnu/libpthread-2.15.so
    fun:_ZN4base17WritePlatformFileEilPKci
    fun:_ZN10disk_cache22SimpleSynchronousEntry9WriteDataEiiPN3net8IOBufferEibPi
 }
 {
-   bug_245092a
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN10disk_cache14Mem*
-   ...
-   fun:_ZN11pnacl_cache31PNaClTranslationCacheWriteEntry12DispatchNextEi
-   fun:_ZN11pnacl_cache31PNaClTranslationCacheWriteEntry9OpenEntryEv
-   fun:_ZN11pnacl_cache31PNaClTranslationCacheWriteEntry5CacheEv
-   fun:_ZN11pnacl_cache21PNaClTranslationCache9StoreNexeERKSsS2_RKN4base8CallbackIFviEEE
-}
-{
-   bug_245092b
-   Memcheck:Leak
-   ...
-   fun:_ZN10disk_cache18CreateCacheBackendEN3net9CacheTypeENS0_11BackendTypeERKN4base8FilePathEibPNS3_16MessageLoopProxyEPNS0_6NetLogEPPNS_7BackendERKNS3_8CallbackIFviEEE
-   fun:_ZN11pnacl_cache21PNaClTranslationCache4InitEN3net9CacheTypeERKN4base8FilePathEiRKNS3_8CallbackIFviEEE
-   ...
-   fun:_ZN11pnacl_cache21PNaClTranslationCache9InitCacheERKN4base8FilePathEbRKNS1_8CallbackIFviEEE
-}
-{
    bug_246148
    Memcheck:Leak
    fun:_Znw*
    ...
    fun:_ZN7content16SiteInstanceImpl10GetProcessEv
    fun:_ZN7content18RenderViewHostImplC1EPNS_12SiteInstanceEPNS_22RenderViewHostDelegateEPNS_24RenderWidgetHostDelegateEiibPNS_23SessionStorageNamespaceE
    fun:_ZN7content21RenderViewHostFactory6CreateEPNS_12SiteInstanceEPNS_22RenderViewHostDelegateEPNS_24RenderWidgetHostDelegateEiibPNS_23SessionStorageNamespaceE
    fun:_ZN7content21RenderViewHostManager4InitEPNS_14BrowserContextEPNS_12SiteInstanceEii
    fun:_ZN7content15WebContentsImpl4InitERKNS_11WebContents12CreateParamsE
    fun:_ZN7content15TestWebContents6CreateEPNS_14BrowserContextEPNS_12SiteInstanceE
@@ skipping 14 matching lines @@
 {
    bug_246306
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN4base8internal20PostTaskAndReplyImpl16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvEEESA_
    fun:_ZN4base10TaskRunner16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvEEES9_
    fun:_ZN6syncer14GetSessionNameERK13scoped_refptrIN4base10TaskRunnerEERKNS1_8CallbackIFvRKSsEEE
    fun:_ZN12browser_sync10DeviceInfo21CreateLocalDeviceInfoEN4base8CallbackIFvRKS0_EEE
    fun:_ZN30ManagedUserRegistrationService8RegisterERKSbItN4base20string16_char_traitsESaItEERKNS0_8CallbackIFvRK22GoogleServiceAuthErrorRKSsEEE
 }