Suppress memcheck leaks and update a TSAN rule.

tools/valgrind/tsan/suppressions.txt

 # There are a few 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 # running overnight and removing outdated bugs/suppressions.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 526 matching lines @@
   ThreadSanitizer:Race
   ...
   fun:frame_thread_free
   ...
   fun:avcodec_close
   ...
   fun:media::FFmpegVideoDecodeEngine::~FFmpegVideoDecodeEngine
   ...
   fun:scoped_ptr::*
   ...
-  fun:media::FFmpegVideoDecoder*Test::~FFmpegVideoDecoder*Test
+  fun:media::FFmpegVideoDecode*Test::~FFmpegVideoDecode*Test
 }
 {
   bug_93932_b
   ThreadSanitizer:Race
   ...
   fun:ff_thread_decode_frame
   fun:avcodec_decode_video2
   ...
   fun:media::FFmpegVideoDecodeEngine::DecodeFrame
   fun:media::FFmpegVideoDecodeEngine::ConsumeVideoSample
@@ skipping 75 matching lines @@
    fun:disk_cache::BackendImpl::MatchEntry
    fun:disk_cache::BackendImpl::InternalDoomEntry
 }
 {
   bug_101853_d
   ThreadSanitizer:Race
   fun:disk_cache::BackendImpl::GetEntryCount
   fun:DiskCacheBackendTest::BackendTrimInvalidEntry2
   fun:DiskCacheBackendTest_*
 }