[Md Feedback] Add initial data population for dialog.

This change populates the feedback dialog with some initial info, including profile email and current URL, by adding a new WebUI Message Handler for C++ <-> JS messaging. The handler will be build out to support more messaging in the future, e.g. system info, screenshots, and feedback submission.

BUG=632112

Review-Url: https://codereview.chromium.org/2190653003
Cr-Commit-Position: refs/heads/master@{#418977}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index af7034c..96a89bd 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -2585,6 +2585,8 @@
       "download/download_shelf.h",
       "download/download_shelf_context_menu.cc",
       "download/download_shelf_context_menu.h",
+      "feedback/feedback_dialog_utils.cc",
+      "feedback/feedback_dialog_utils.h",
       "feedback/feedback_profile_observer.cc",
       "feedback/feedback_profile_observer.h",
       "feedback/show_feedback_page.cc",