Factor out dependncy on download throttling from core download code.

chrome/chrome_browser.gypi

Index: chrome/chrome_browser.gypi
===================================================================
--- chrome/chrome_browser.gypi	(revision 96872)
+++ chrome/chrome_browser.gypi	(working copy)
@@ -868,12 +868,16 @@
         'browser/download/download_request_infobar_delegate.h',
         'browser/download/download_request_limiter.cc',
         'browser/download/download_request_limiter.h',
+        'browser/download/download_request_limiter_observer.cc',
+        'browser/download/download_request_limiter_observer.h',
         'browser/download/download_safe_browsing_client.cc',
         'browser/download/download_safe_browsing_client.h',
         'browser/download/download_shelf.h',
         'browser/download/download_shelf_context_menu.cc',
         'browser/download/download_shelf_context_menu.h',
         'browser/download/download_started_animation.h',
+        'browser/download/download_throttling_resource_handler.cc',
+        'browser/download/download_throttling_resource_handler.h',
         'browser/download/download_util.cc',
         'browser/download/download_util.h',
         'browser/download/drag_download_file.cc',
@@ -1867,8 +1871,6 @@
         'browser/renderer_host/chrome_render_view_host_observer.h',
         'browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc',
         'browser/renderer_host/chrome_resource_dispatcher_host_delegate.h',
-        'browser/renderer_host/download_throttling_resource_handler.cc',
-        'browser/renderer_host/download_throttling_resource_handler.h',
         'browser/renderer_host/gtk_im_context_wrapper.cc',
         'browser/renderer_host/gtk_im_context_wrapper.h',
         'browser/renderer_host/gtk_key_bindings_handler.cc',