Populate stack frames with unloaded module info.

This CL hits lots of source files because:
 1. An update to the CodeModule virtual class. I added an is_loaded
  method to specify whether the module is loaded. There were several
  mocks/test classes that needed to be updated with an implementation.
  An alternative to this route would be to modify
  MinidumpUnloadedModule::code_file to prepend "Unloaded_" to the
  module name.

 2. Added an unloaded_modules parameter to
  StackFrameSymbolizer::FillSourceLineInfo.

BUG=

Change-Id: Ic9c7f7c7b7e932a154a5d4ccf292c1527d8da09f
Reviewed-on: https://chromium-review.googlesource.com/430241
Reviewed-by: Ivan Penkov <ivanpe@chromium.org>

src/processor/process_state.cc

@@ -64,6 +64,7 @@ void ProcessState::Clear() {
   modules_with_corrupt_symbols_.clear();
   delete modules_;
   modules_ = NULL;
+  unloaded_modules_ = NULL;
 }
 
 }  // namespace google_breakpad