Add heapcheck suppression for audio device enumeration leak

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 # running overnight and removing outdated bugs/suppressions.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 248 matching lines @@
    fun:*ScopedTestNSSDB
 }
 {
    bug_156433_b
    Heapcheck:Leak
    fun:PORT_Alloc_Util
    fun:crypto::::NSSInitSingleton::OpenUserDB
    fun:crypto::::NSSInitSingleton::OpenTestNSSDB
    fun:*ScopedTestNSSDB
 }
+{
+   bug_156829
+   Heapcheck:Leak
+   ...
+   fun:media_stream::AudioInputDeviceManager::EnumerateOnDeviceThread
+}
 
 
 #-----------------------------------------------------------------------
 # 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
 {
    Heapcheck sanity test (ToolsSanityTest.MemoryLeak).
    Heapcheck:Leak
    fun:base::ToolsSanityTest_MemoryLeak_Test::TestBody
 }
@@ skipping 1297 matching lines @@
    Heapcheck:Leak
    ...
    fun:TestURLRequestContext::Init
    fun:TestURLRequestContext::TestURLRequestContext
    fun:TestURLRequestContextGetter::GetURLRequestContext
    fun:predictors::TestResourcePrefetcherDelegate::GetURLRequestContext
    fun:predictors::ResourcePrefetcher::SendRequest
    fun:predictors::ResourcePrefetcher::TryToLaunchPrefetchRequests
    fun:predictors::ResourcePrefetcher::Start
 }