Add support for Location (RTC_FROM_HERE) to ProcessThread::RegisterModule.

This makes a few things a lot clearer when looking at perf trace data:

* What module instances (where they were created) are called
* On what thread
* How frequently
* For how long

ProcessThread will be replaced by TaskQueue moving forward and this is a step towards understanding the behavior of the affected code.

BUG=webrtc:7219

Review-Url: https://codereview.webrtc.org/2729053002
Cr-Commit-Position: refs/heads/master@{#16998}

webrtc/modules/utility/include/process_thread.h

@@ -25,6 +25,10 @@ class QueuedTask;
 }
 #endif
 
+namespace rtc {
+class Location;
+}
+
 namespace webrtc {
 class Module;
 
@@ -61,7 +65,7 @@ class ProcessThread {
 
   // Adds a module that will start to receive callbacks on the worker thread.
   // Can be called from any thread.
-  virtual void RegisterModule(Module* module) = 0;
+  virtual void RegisterModule(Module* module, const rtc::Location& from) = 0;
 
   // Removes a previously registered module.
   // Can be called from any thread.