mkvmuxer: Set default doc type version to 4.

mkvmuxer can write matroska v4 elements in all modes, but does
not always confirm that the doc type is high enough for all
elements written. The main culprits are Colour and its
children. Avoid problems by using 4 as the default version.
This avoids problems in all cases but those where users who
know what they are doing have written the EBML header manually.

Update the test files because the new default causes the file
compare abuse in the muxer tests to fail.

Update expected doc type version in the parsing tests.

BUG=webm:1201

Change-Id: I4c69000af4c1d5efe66315c17f3953344ef04993
diff --git a/common/vp9_header_parser_tests.cc b/common/vp9_header_parser_tests.cc
index 1924f27..c4610b9 100644
--- a/common/vp9_header_parser_tests.cc
+++ b/common/vp9_header_parser_tests.cc
@@ -56,7 +56,7 @@
   }
 
   void CreateAndLoadSegment(const std::string& filename) {
-    CreateAndLoadSegment(filename, 2);
+    CreateAndLoadSegment(filename, 4);
   }
 
   void ProcessTheFrames() {
diff --git a/common/vp9_level_stats_tests.cc b/common/vp9_level_stats_tests.cc
index 4653b7a..84210ae 100644
--- a/common/vp9_level_stats_tests.cc
+++ b/common/vp9_level_stats_tests.cc
@@ -57,7 +57,7 @@
   }
 
   void CreateAndLoadSegment(const std::string& filename) {
-    CreateAndLoadSegment(filename, 2);
+    CreateAndLoadSegment(filename, 4);
   }
 
   void ProcessTheFrames() {
diff --git a/mkvmuxer/mkvmuxer.h b/mkvmuxer/mkvmuxer.h
index 9a34776..7cb0636 100644
--- a/mkvmuxer/mkvmuxer.h
+++ b/mkvmuxer/mkvmuxer.h
@@ -1304,7 +1304,7 @@
     kBeforeClusters = 0x1  // Position Cues before Clusters
   };
 
-  const static uint32_t kDefaultDocTypeVersion = 2;
+  const static uint32_t kDefaultDocTypeVersion = 4;
   const static uint64_t kDefaultMaxClusterDuration = 30000000000ULL;
 
   Segment();
diff --git a/testing/parser_tests.cc b/testing/parser_tests.cc
index 1d92798..e5d88ba 100644
--- a/testing/parser_tests.cc
+++ b/testing/parser_tests.cc
@@ -81,7 +81,7 @@
   }
 
   bool CreateAndLoadSegment(const std::string& filename) {
-    return CreateAndLoadSegment(filename, 2);
+    return CreateAndLoadSegment(filename, 4);
   }
 
   void CompareBlockContents(const Cluster* const cluster,
diff --git a/testing/testdata/accurate_cluster_duration.webm b/testing/testdata/accurate_cluster_duration.webm
index 6c8b59e..fffe83d 100644
--- a/testing/testdata/accurate_cluster_duration.webm
+++ b/testing/testdata/accurate_cluster_duration.webm
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diff --git a/testing/testdata/accurate_cluster_duration_last_frame.webm b/testing/testdata/accurate_cluster_duration_last_frame.webm
index 159f5b2..8104bfc 100644
--- a/testing/testdata/accurate_cluster_duration_last_frame.webm
+++ b/testing/testdata/accurate_cluster_duration_last_frame.webm
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diff --git a/testing/testdata/accurate_cluster_duration_two_tracks.webm b/testing/testdata/accurate_cluster_duration_two_tracks.webm
index 3f3677c..cf69859 100644
--- a/testing/testdata/accurate_cluster_duration_two_tracks.webm
+++ b/testing/testdata/accurate_cluster_duration_two_tracks.webm
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diff --git a/testing/testdata/block_with_additional.webm b/testing/testdata/block_with_additional.webm
index db67ab4..2f1b22c 100644
--- a/testing/testdata/block_with_additional.webm
+++ b/testing/testdata/block_with_additional.webm
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diff --git a/testing/testdata/chapters.webm b/testing/testdata/chapters.webm
index 3d1f01b..af0c5fe 100644
--- a/testing/testdata/chapters.webm
+++ b/testing/testdata/chapters.webm
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diff --git a/testing/testdata/cues_before_clusters.webm b/testing/testdata/cues_before_clusters.webm
index 166bd87..c634b17 100644
--- a/testing/testdata/cues_before_clusters.webm
+++ b/testing/testdata/cues_before_clusters.webm
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diff --git a/testing/testdata/fixed_size_cluster_timecode.webm b/testing/testdata/fixed_size_cluster_timecode.webm
index ecf956d..c6f1cc6 100644
--- a/testing/testdata/fixed_size_cluster_timecode.webm
+++ b/testing/testdata/fixed_size_cluster_timecode.webm
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diff --git a/testing/testdata/force_new_cluster.webm b/testing/testdata/force_new_cluster.webm
index b0923e3..f762b07 100644
--- a/testing/testdata/force_new_cluster.webm
+++ b/testing/testdata/force_new_cluster.webm
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diff --git a/testing/testdata/matroska_doctype.mkv b/testing/testdata/matroska_doctype.mkv
index 4907f3d..5652785 100644
--- a/testing/testdata/matroska_doctype.mkv
+++ b/testing/testdata/matroska_doctype.mkv
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diff --git a/testing/testdata/max_cluster_duration.webm b/testing/testdata/max_cluster_duration.webm
index 01f172f..9caad9c 100644
--- a/testing/testdata/max_cluster_duration.webm
+++ b/testing/testdata/max_cluster_duration.webm
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diff --git a/testing/testdata/max_cluster_size.webm b/testing/testdata/max_cluster_size.webm
index 5f7d033..df87536 100644
--- a/testing/testdata/max_cluster_size.webm
+++ b/testing/testdata/max_cluster_size.webm
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diff --git a/testing/testdata/metadata_block.webm b/testing/testdata/metadata_block.webm
index 35cc02c..a9c686e 100644
--- a/testing/testdata/metadata_block.webm
+++ b/testing/testdata/metadata_block.webm
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diff --git a/testing/testdata/output_cues.webm b/testing/testdata/output_cues.webm
index 69bcd93..49e2126 100644
--- a/testing/testdata/output_cues.webm
+++ b/testing/testdata/output_cues.webm
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diff --git a/testing/testdata/segment_duration.webm b/testing/testdata/segment_duration.webm
index eea3ec7..47cfb6d 100644
--- a/testing/testdata/segment_duration.webm
+++ b/testing/testdata/segment_duration.webm
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diff --git a/testing/testdata/segment_info.webm b/testing/testdata/segment_info.webm
index d67acaf..0fde8f0 100644
--- a/testing/testdata/segment_info.webm
+++ b/testing/testdata/segment_info.webm
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diff --git a/testing/testdata/set_cues_track_number.webm b/testing/testdata/set_cues_track_number.webm
index f2a6170..82a2b38 100644
--- a/testing/testdata/set_cues_track_number.webm
+++ b/testing/testdata/set_cues_track_number.webm
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diff --git a/testing/testdata/simple_block.webm b/testing/testdata/simple_block.webm
index 43ddd88..c311e68 100644
--- a/testing/testdata/simple_block.webm
+++ b/testing/testdata/simple_block.webm
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diff --git a/testing/testdata/test_stereo_left_right.webm b/testing/testdata/test_stereo_left_right.webm
index 7358435..8c717dc 100644
--- a/testing/testdata/test_stereo_left_right.webm
+++ b/testing/testdata/test_stereo_left_right.webm
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diff --git a/testing/testdata/tracks.webm b/testing/testdata/tracks.webm
index 7572e67..8aa9274 100644
--- a/testing/testdata/tracks.webm
+++ b/testing/testdata/tracks.webm
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diff --git a/testing/testdata/webm_doctype.webm b/testing/testdata/webm_doctype.webm
index 3fdab89..4269030 100644
--- a/testing/testdata/webm_doctype.webm
+++ b/testing/testdata/webm_doctype.webm
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