Expand suppressions for v8 external strings being leaked, due to no GC.

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 # running overnight and removing outdated bugs/suppressions.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 661 matching lines @@
    ...
    fun:net::::ProxyResolverV8WithMockBindings::SetPacScriptFromDisk
 }
 {
    bug_67378_b
    Heapcheck:Leak
    ...
    fun:net::::LoadScriptData
 }
 {
+   bug_67378_c
+   Heapcheck:Leak
+   fun:net::::ASCIILiteralToV8String
+   fun:net::ProxyResolverV8::Context::InitV8
+   fun:net::ProxyResolverV8::SetPacScript
+}
+{
+   bug_67378_d
+   Heapcheck:Leak
+   fun:net::::ScriptDataToV8String
+   fun:net::ProxyResolverV8::Context::InitV8
+   fun:net::ProxyResolverV8::SetPacScript
+}
+{
    bug_68304
    Heapcheck:Leak
    ...
    fun:IPC::ParamTraits::Read
    fun:IPC::ReadParam
    fun:IPC::MessageWithTuple::Read
    fun:IPC::MessageWithTuple::Dispatch
    fun:ResourceDispatcherHost::OnMessageReceived
    fun:ResourceDispatcherHostTest::MakeTestRequest
 }
@@ skipping 1139 matching lines @@
    fun:AutofillPopupControllerUnitTest::AutofillPopupControllerUnitTest
    fun:AutofillPopupControllerUnitTest_GrowPopupInSpace_Test::AutofillPopupControllerUnitTest_GrowPopupInSpace_Test
    fun:testing::internal::TestFactoryImpl::CreateTest
 }
 {
    bug_171983
    Heapcheck:Leak
    ...
    fun:chromeos::MagnificationManagerTest_MagnificationObserver_Test::TestBody
 }