(De)-serialize BeginMainFrameAndCommitState to protobuf.

BUG=550687
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1581773002

Cr-Commit-Position: refs/heads/master@{#369836}

diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 353958d..50f7858f 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn

@@ -317,6 +317,8 @@
     "playback/largest_display_item.h",
     "playback/transform_display_item.cc",
     "playback/transform_display_item.h",
+    "proto/base_conversions.cc",
+    "proto/base_conversions.h",
     "proto/cc_conversions.cc",
     "proto/cc_conversions.h",
     "proto/gfx_conversions.cc",
@@ -838,6 +840,7 @@
     "playback/display_item_list_unittest.cc",
     "playback/display_list_raster_source_unittest.cc",
     "playback/display_list_recording_source_unittest.cc",
+    "proto/base_conversions_unittest.cc",
     "proto/cc_conversions_unittest.cc",
     "proto/gfx_conversions_unittest.cc",
     "proto/gpu_conversions_unittest.cc",
@@ -900,6 +903,7 @@
     "trees/occlusion_tracker_unittest.cc",
     "trees/occlusion_unittest.cc",
     "trees/property_tree_unittest.cc",
+    "trees/proxy_common_unittest.cc",
     "trees/proxy_impl_unittest.cc",
     "trees/threaded_channel_unittest.cc",
     "trees/tree_synchronizer_unittest.cc",