Adding unittest for the reference counting of WebMediaStreamDescriptor/Source

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 # running overnight and removing outdated bugs/suppressions.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 1697 matching lines @@
    fun:PluginService::RegisterPepperPlugins
    fun:PluginService::Init
    fun:chromeos::::GViewRequestInterceptorTest::SetUp
 }
 {
    bug_105624_a
    Heapcheck:Leak
    fun:PeerConnectionHandlerTest_Basic_Test::TestBody
 }
 {
-   bug_105624_b
-   Heapcheck:Leak
-   fun:WTF::fastMalloc
-   fun:WTF::RefCounted::operator new
-   fun:WebCore::MediaStreamSource::create
-   fun:WebKit::WebMediaStreamSource::initialize
-   fun:PeerConnectionHandlerTest_Basic_Test::TestBody
-}
-{
    bug_105624_c
    Heapcheck:Leak
    fun:WTF::fastMalloc
    fun:WTF::StringImpl::createUninitialized
    fun:WTF::String::fromUTF8
    ...
    fun:WebKit::WebString::fromUTF8
    ...
    fun:PeerConnectionHandlerTest_Basic_Test::TestBody
 }
@@ skipping 86 matching lines @@
    fun:IPC::ParamTraits::Read
    fun:IPC::ReadParam
    fun:IPC::MessageSchema::Read
    fun:ResourceHostMsg_RequestResource::Read
    fun:ResourceHostMsg_RequestResource::Dispatch
    fun:ResourceDispatcherHost::OnMessageReceived
    fun:ResourceDispatcherHostTest::MakeTestRequest
    fun:ResourceDispatcherHostTest::MakeTestRequest
    fun:ResourceDispatcherHostTest_*_Test::TestBody
 }
-{
-   bug_111757
-   Heapcheck:Leak
-   fun:WTF::fastMalloc
-   ...
-   fun:PeerConnectionHandler::CreateWebKitStreamDescriptor
-   fun:PeerConnectionHandler::OnAddStreamCallback
-   fun:PeerConnectionHandler::OnAddStream
-   fun:PeerConnectionHandlerTest_Basic_Test::TestBody
-}