Move creation and ownership of HostZoomMap to content instead of having every embedder do this.

content/browser/renderer_host/async_resource_handler.cc

Index: content/browser/renderer_host/async_resource_handler.cc
===================================================================
--- content/browser/renderer_host/async_resource_handler.cc	(revision 122827)
+++ content/browser/renderer_host/async_resource_handler.cc	(working copy)
@@ -29,6 +29,7 @@
 
 using base::TimeTicks;
 using content::GlobalRequestID;
+using content::HostZoomMap;
 
 namespace {
 
@@ -134,7 +135,8 @@
   DevToolsNetLogObserver::PopulateResponseInfo(request, response);
 
   content::ResourceContext* resource_context = filter_->resource_context();
-  content::HostZoomMap* host_zoom_map = resource_context->GetHostZoomMap();
+  content::HostZoomMap* host_zoom_map =
+      HostZoomMap::GetForResourceContext(resource_context);
 
   ResourceDispatcherHostRequestInfo* info = rdh_->InfoForRequest(request);
   if (info->resource_type() == ResourceType::MAIN_FRAME && host_zoom_map) {