Initial commit for chrome.launcherSearchProvider API.

This CL includes
- Define API idl.
- Add permission.
- Add flag.
- Implement onQueryStarted event.

Permission is restricted to trunk and FileManager during the development.
After the implementation is completed, it will be relaxed to white-listed on stable and public on dev.

BUG=440649

Review URL: https://codereview.chromium.org/1011353003

Cr-Commit-Position: refs/heads/master@{#323434}
diff --git a/extensions/browser/extension_function_histogram_value.h b/extensions/browser/extension_function_histogram_value.h
index a9cff51d..e37b8dbd 100644
--- a/extensions/browser/extension_function_histogram_value.h
+++ b/extensions/browser/extension_function_histogram_value.h
@@ -1053,6 +1053,7 @@
   EASYUNLOCKPRIVATE_HIDEERRORBUBBLE,
   WEBVIEWINTERNAL_SETZOOMMODE,
   WEBVIEWINTERNAL_GETZOOMMODE,
+  LAUNCHERSEARCHPROVIDER_SETSEARCHRESULTS,
   // Last entry: Add new entries above and ensure to update
   // tools/metrics/histograms/histograms.xml.
   ENUM_BOUNDARY