Bug 1182996 - Fix and add missing namespace comments. rs=ehsan

The bulk of this commit was generated by running:

  run-clang-tidy.py \
    -checks='-*,llvm-namespace-comment' \
    -header-filter=^/.../mozilla-central/.* \
    -fix

dom/plugins/ipc/PluginModuleParent.cpp

@@ -358,7 +358,7 @@ PRCList PluginModuleMapping::sModuleListHead =
 
 bool PluginModuleMapping::sIsLoadModuleOnStack = false;
 
-} // anonymous namespace
+} // namespace
 
 void
 mozilla::plugins::TerminatePlugin(uint32_t aPluginId,
@@ -958,7 +958,7 @@ GetProcessCpuUsage(const InfallibleTArray<base::ProcessHandle>& processHandles,
   return true;
 }
 
-} // anonymous namespace
+} // namespace
 
 #endif // #ifdef XP_WIN