rule-based: Deprecate |alt| and |ctrl| in keypress info.

These aren't actually used in rule-based engine. No point sending them.

Bug: 1009903
Change-Id: Ic0add4ecba3d4341c2976f6abce8e9c86465d116
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1833032Reviewed-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701472}

chromeos/services/ime/public/mojom/input_engine.mojom

@@ -44,7 +44,6 @@ struct KeypressResponseForRulebased {
 
 // Information about a specific keypress.
 struct KeypressInfoForRulebased {
-
   // Keypress Type (Eg; "keydown", "keyup", etc).
   string type;
 
@@ -55,8 +54,8 @@ struct KeypressInfoForRulebased {
   bool shift;
   bool altgr;
   bool caps;
-  bool ctrl;
-  bool alt;
+  bool ctrl = false; // DEPRECATED
+  bool alt = false; // DEPRECATED
 };
 
 // Manages access to a set of IME engines, implemented by the IME service