Report parse error for WebM clusters missing a timecode

Replaces a DCHECK with parse error when parsing a WebM
cluster that has no timecode. This supplements the existing
WebMClusterParser::OnBlock() logic that similarly indicates
parse error when processing blocks. However, if there were
no blocks in the cluster, then the DCHECK could have been
hit if there were no timecode.

R=acolwell@chromium.org
BUG=335344
TEST=(local Linux) All media_unittests pass including the new ones

Review URL: https://codereview.chromium.org/141013008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245608 0039d316-1c4b-4281-b951-d872f2087c98

media/webm/webm_cluster_parser.cc

@@ -110,7 +110,11 @@ int WebMClusterParser::Parse(const uint8* buf, int size) {
     // If there were no buffers in this cluster, set the cluster start time to
     // be the |cluster_timecode_|.
     if (cluster_start_time_ == kNoTimestamp()) {
-      DCHECK_GT(cluster_timecode_, -1);
+      // If the cluster did not even have a |cluster_timecode_|, signal parse
+      // error.
+      if (cluster_timecode_ < 0)
+        return -1;
+
       cluster_start_time_ = base::TimeDelta::FromMicroseconds(
           cluster_timecode_ * timecode_multiplier_);
     }

media/webm/webm_cluster_parser_unittest.cc

@@ -525,4 +525,21 @@ TEST_F(WebMClusterParserTest, ParseBadEncryptedBlock) {
   EXPECT_EQ(-1, result);
 }
 
+TEST_F(WebMClusterParserTest, ParseInvalidZeroSizedCluster) {
+  const uint8 kBuffer[] = {
+    0x1F, 0x43, 0xB6, 0x75, 0x80,  // CLUSTER (size = 0)
+  };
+
+  EXPECT_EQ(parser_->Parse(kBuffer, sizeof(kBuffer)), -1);
+}
+
+TEST_F(WebMClusterParserTest, ParseInvalidUnknownButActuallyZeroSizedCluster) {
+  const uint8 kBuffer[] = {
+    0x1F, 0x43, 0xB6, 0x75, 0xFF,  // CLUSTER (size = "unknown")
+    0x1F, 0x43, 0xB6, 0x75, 0x85,  // CLUSTER (size = 5)
+  };
+
+  EXPECT_EQ(parser_->Parse(kBuffer, sizeof(kBuffer)), -1);
+}
+
 }  // namespace media