Log MediaSource parsing errors to the MediaLog so they can appear in chrome:media-internals.

media/base/media_log.h

Index: media/base/media_log.h
diff --git a/media/base/media_log.h b/media/base/media_log.h
index 3ad2c0b7b1cbc42c2ec73ad6be8b00e3a1a810af..e2a05bc3932c3702692104bfc1e68bc3f21cb297 100644
--- a/media/base/media_log.h
+++ b/media/base/media_log.h
@@ -5,6 +5,9 @@
 #ifndef MEDIA_BASE_MEDIA_LOG_H_
 #define MEDIA_BASE_MEDIA_LOG_H_
 
+#include <sstream>
+#include <string>
+
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
@@ -14,6 +17,25 @@
 
 namespace media {
 
+// Indicates an error string should be added to the error log.
+// First parameter - The string to add to the error log.
+typedef base::Callback<void(const std::string&)> ErrorLogCB;
+
+// Helper class to make it easier to use error_cb like DVLOG().
+class ErrorLogHelper {

[scherkus (not reviewing), 2012/12/07 20:40:11]

WDYT about dropping "Error" from everything?

not only do we save characters but it doesn't preclude using it for non-error
related messages

+ public:
+  ErrorLogHelper(const ErrorLogCB& error_cb);
+  ~ErrorLogHelper();
+
+  std::ostream& stream() { return stream_; }
+
+ private:
+  ErrorLogCB error_cb_;
+  std::stringstream stream_;
+};
+
+#define ERROR_LOG(error_cb) ErrorLogHelper(error_cb).stream()
+
 class MEDIA_EXPORT MediaLog : public base::RefCountedThreadSafe<MediaLog> {
  public:
   // Convert various enums to strings.
@@ -43,6 +65,8 @@ class MEDIA_EXPORT MediaLog : public base::RefCountedThreadSafe<MediaLog> {
       size_t width, size_t height);
   scoped_ptr<MediaLogEvent> CreateBufferedExtentsChangedEvent(
       size_t start, size_t current, size_t end);
+  scoped_ptr<MediaLogEvent> CreateMediaSourceErrorEvent(
+      const std::string& error);
 
  protected:
   friend class base::RefCountedThreadSafe<MediaLog>;