Fix memory leak in AutocompleteProviderTest::GetDestinationURL unit test.

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 # running overnight and removing outdated bugs/suppressions.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 6505 matching lines @@
    fun:_ZN3gpu5gles2*Immediate4InitE*
    fun:_ZN3gpu5gles2*GLES2ImplementationTest_*_Test8TestBodyEv
 }
 {
    bug_175100
    Memcheck:Leak
    ...
    fun:_ZN20OneClickSigninHelper14DidStopLoadingEPN7content14RenderViewHostE
    fun:_ZN67OneClickSigninHelperTest_SigninFromWebstoreWithConfigSyncfirst_Test8TestBodyEv
 }
-{
-   bug_175428:
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN22AutocompleteControllerC1EP7ProfileP30AutocompleteControllerDelegatei
-   fun:_ZN24AutocompleteProviderTest32ResetControllerWithTestProvidersEbPP12TestProviderS2_
-}