Fix memory leak in AutocompleteProviderTest::GetDestinationURL unit test.

tools/heapcheck/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 # running overnight and removing outdated bugs/suppressions.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 1759 matching lines @@
 }
 {
    bug_175100
    Heapcheck:Leak
    ...
    fun:::StartSync
    fun:OneClickSigninHelper::DidStopLoading
    fun:OneClickSigninHelperTest_SigninFromWebstoreWithConfigSyncfirst_Test::TestBody
 }
 {
-  bug_175428:
-  Heapcheck:Leak
-  fun:AutocompleteController::AutocompleteController
-  fun:AutocompleteProviderTest::ResetControllerWithTestProviders
-}
-{
    bug_175435:
    Heapcheck:Leak
    ...
    fun:::StartSync
    fun:::StartExplicitSync
    fun:OneClickSigninHelper::DidStopLoading
 }