blimp: Add logging for compositor and render widget feature.

blimp/engine/app/blimp_content_main_delegate.cc

Index: blimp/engine/app/blimp_content_main_delegate.cc
diff --git a/blimp/engine/app/blimp_content_main_delegate.cc b/blimp/engine/app/blimp_content_main_delegate.cc
index 6fe0b41493ac7d7667cc37bc26d3752570e06813..265f368a4b0a8e6ca658ec31e530cc81b1956082 100644
--- a/blimp/engine/app/blimp_content_main_delegate.cc
+++ b/blimp/engine/app/blimp_content_main_delegate.cc
@@ -4,6 +4,7 @@
 
 #include "blimp/engine/app/blimp_content_main_delegate.h"
 
+#include "base/command_line.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ -17,6 +18,13 @@ namespace blimp {
 namespace engine {
 namespace {
 void InitLogging() {
+  // TODO(haibinlu): Remove this before release.
+  // Enables a few verbose log by default.
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch("vmodule")) {
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        "vmodule", "remote_channel_main=1");

[haibinlu, 2016/03/30 18:37:08]

Do we need this? since we have reliable message delivery, main&impl message
exchange will be logged twice, one in Engine and once in Client, and they have
the same info.

[Khushal, 2016/03/30 18:55:47]

A message might be dropped if it exceeds the limit. Also, there might be an
error during the begin main frame and serialization step, would help in
debugging to know what the state the engine compositor was at when an error
occurred.

+  }
+
   logging::LoggingSettings settings;
   base::FilePath log_filename;
   PathService::Get(base::DIR_EXE, &log_filename);