Add RTC_ prefix to (D)CHECKs and related macros.

webrtc/base/checks.cc

Index: webrtc/base/checks.cc
diff --git a/webrtc/base/checks.cc b/webrtc/base/checks.cc
index b85af1ed179995588fecdbade9b2623311e7ce69..49a31f29b9df4e4d6bca59e4d5f338a5a15ae802 100644
--- a/webrtc/base/checks.cc
+++ b/webrtc/base/checks.cc
@@ -109,9 +109,6 @@ void FatalMessage::Init(const char* file, int line) {
           << file << ", line " << line << std::endl << "# ";
 }
 
-// Refer to comments in checks.h.
-#ifndef WEBRTC_CHROMIUM_BUILD
-
 // MSVC doesn't like complex extern templates and DLLs.
 #if !defined(COMPILER_MSVC)
 // Explicit instantiations for commonly used comparisons.
@@ -127,6 +124,4 @@ template std::string* MakeCheckOpString<std::string, std::string>(
     const std::string&, const std::string&, const char* name);
 #endif
 
-#endif  // WEBRTC_CHROMIUM_BUILD
-
 }  // namespace rtc