Bug 1375392 - Tweak the PROFILER_LABEL* macros. r=mstange.

This patch makes the following changes to the macros.

- Removes PROFILER_LABEL_FUNC. It's only suitable for use in functions outside
  classes, due to PROFILER_FUNCTION_NAME not getting class names, and it was
  mostly misused.

- Removes PROFILER_FUNCTION_NAME. It's no longer used, and __func__ is
  universally available now anyway.

- Combines the first two string literal arguments of PROFILER_LABEL and
  PROFILER_LABEL_DYNAMIC into a single argument. There was no good reason for
  them to be separate, and it forced a '::' in the label, which isn't always
  appropriate. Also, the meaning of the "name_space" argument was interpreted
  in an interesting variety of ways.

- Adds an "AUTO_" prefix to PROFILER_LABEL and PROFILER_LABEL_DYNAMIC, to make
  it clearer they construct RAII objects rather than just being function calls.
  (I myself have screwed up the scoping because of this in the past.)

- Fills in the 'js::ProfileEntry::Category::' qualifier within the macro, so
  the caller doesn't need to. This makes a *lot* more of the uses fit onto a
  single line.

The patch also makes the following changes to the macro uses (beyond those
required by the changes described above).

- Fixes a bunch of labels that had gotten out of sync with the name of the
  class and/or function that encloses them.

- Removes a useless PROFILER_LABEL use within a trivial scope in
  EventStateManager::DispatchMouseOrPointerEvent(). It clearly wasn't serving
  any useful purpose. It also serves as extra evidence that the AUTO_ prefix is
  a good idea.

- Tweaks DecodePool::SyncRunIf{Preferred,Possible} so that the labelling is
  done within them, instead of at their callsites, because that's a more
  standard way of doing things.

dom/plugins/base/nsNPAPIPluginInstance.cpp

@@ -225,7 +225,7 @@ nsNPAPIPluginInstance::StopTime()
 
 nsresult nsNPAPIPluginInstance::Initialize(nsNPAPIPlugin *aPlugin, nsPluginInstanceOwner* aOwner, const nsACString& aMIMEType)
 {
-  PROFILER_LABEL_FUNC(js::ProfileEntry::Category::OTHER);
+  AUTO_PROFILER_LABEL("nsNPAPIPlugin::Initialize", OTHER);
   PLUGIN_LOG(PLUGIN_LOG_NORMAL, ("nsNPAPIPluginInstance::Initialize this=%p\n",this));
 
   NS_ENSURE_ARG_POINTER(aPlugin);
@@ -590,7 +590,7 @@ nsresult nsNPAPIPluginInstance::HandleEvent(void* event, int16_t* result,
   if (RUNNING != mRunning)
     return NS_OK;
 
-  PROFILER_LABEL_FUNC(js::ProfileEntry::Category::OTHER);
+  AUTO_PROFILER_LABEL("nsNPAPIPluginInstance::HandleEvent", OTHER);
 
   if (!event)
     return NS_ERROR_FAILURE;