Mash: Replaces "exe:chrome" with "service:content_browser"

No more references to exe:chrome, instead anyone wanting browser
interfaces connects to service:content_browser, which is consistent
with the rest of the universe.

ServiceManager and Catalog have some control interfaces added to
override path resolution for executables and manifests. MashRunner
uses this to direct resolution of "exe:chrome_mash" and
"service:content_browser" accordingly, as well as to resolve
content process manifests to chrome's/mash's overlayed versions
on disk.

Also changes the service_manifest GN template to support overlays.
This makes it easy to reuse the existing overlay metadata with
standalone ServiceManager, as well as to layer multiple overlays
(e.g. content_browser + chrome_content_browser + chrome_mash_content_browser).

Adds a browser manifest overlay specifically for Mash, which is
applied on top of Chrome's own overlay.

BUG=646077
TEST=chrome --mash seems to "work", can set wallpaper, browse cat photos, run task_viewer, etc

Review-Url: https://codereview.chromium.org/2389133008
Cr-Commit-Position: refs/heads/master@{#423803}
diff --git a/chrome/browser/browser_resources.grd b/chrome/browser/browser_resources.grd
index d956300..8a75db78 100644
--- a/chrome/browser/browser_resources.grd
+++ b/chrome/browser/browser_resources.grd
@@ -595,6 +595,7 @@
       </if>
       <include name="IDR_CHROME_CONTENT_BROWSER_MANIFEST_OVERLAY" file="chrome_content_browser_manifest_overlay.json" type="BINDATA" />
       <include name="IDR_CHROME_CONTENT_GPU_MANIFEST_OVERLAY" file="chrome_content_gpu_manifest_overlay.json" type="BINDATA" />
+      <include name="IDR_CHROME_CONTENT_RENDERER_MANIFEST_OVERLAY" file="chrome_content_renderer_manifest_overlay.json" type="BINDATA" />
       <include name="IDR_CHROME_CONTENT_UTILITY_MANIFEST_OVERLAY" file="chrome_content_utility_manifest_overlay.json" type="BINDATA" />
     </includes>
   </release>