Mac: Refine ui_controls_mac's SynthesizeKeyEvent()

ui/base/test/ui_controls_mac.mm

Index: ui/base/test/ui_controls_mac.mm
diff --git a/ui/base/test/ui_controls_mac.mm b/ui/base/test/ui_controls_mac.mm
index 1308de0cb4f0309db17f0b4ab74b2477704e7e6e..5689518ec399e3ffdfa0ed61a73a6e950db59f03 100644
--- a/ui/base/test/ui_controls_mac.mm
+++ b/ui/base/test/ui_controls_mac.mm
@@ -96,13 +96,29 @@ NSEvent* SynthesizeKeyEvent(NSWindow* window,
   // Note that, in line with AppKit's documentation (and tracing "real" events),
   // -[NSEvent charactersIngoringModifiers]" are "the characters generated by
   // the receiving key event as if no modifier key (except for Shift)".
-  // So |charactersIgnoringModifiers| uses |shifted_characters|, while
-  // |characters| uses keyboard characters.
+  // So |charactersIgnoringModifiers| uses |shifted_character|.
   NSString* charactersIgnoringModifiers =
       [[[NSString alloc] initWithCharacters:&shifted_character
                                      length:1] autorelease];
-  NSString* characters =
-      [[[NSString alloc] initWithCharacters:&character length:1] autorelease];
+  NSString* characters;
+  // The following were determined empirically on OSX 10.9.
+  if (flags & NSControlKeyMask) {
+    // If Ctrl is pressed, Cocoa always puts an empty string into |characters|.
+    characters = [NSString string];
+  } else if (flags & NSCommandKeyMask) {
+    // If Cmd is pressed, Cocoa puts a lowercase character into |characters|,
+    // regardless of Shift. If, however, Alt is also pressed then shift *is*
+    // preserved, but re-mappings for Alt are not implemented. Although we still
+    // need to support Alt for things like Alt+Left/Right which don't care.
+    characters =
+        [[[NSString alloc] initWithCharacters:&character length:1] autorelease];
+  } else {
+    // If just Shift or nothing is pressed, |characters| will match
+    // |charactersIgnoringModifiers|. Alt puts a special character into
+    // |characters| (not |charactersIgnoringModifiers|), but they're not mapped
+    // here.
+    characters = charactersIgnoringModifiers;
+  }
 
   NSEventType type = (keyDown ? NSKeyDown : NSKeyUp);
 
@@ -115,17 +131,16 @@ NSEvent* SynthesizeKeyEvent(NSWindow* window,
   // For events other than mouse moved, [event locationInWindow] is
   // UNDEFINED if the event is not NSMouseMoved.  Thus, the (0,0)
   // location should be fine.
-  NSEvent* event =
-      [NSEvent keyEventWithType:type
-                       location:NSZeroPoint
-                  modifierFlags:flags
-                      timestamp:TimeIntervalSinceSystemStartup()
-                   windowNumber:[window windowNumber]
-                        context:nil
-                     characters:characters
-    charactersIgnoringModifiers:charactersIgnoringModifiers
-                      isARepeat:NO
-                        keyCode:(unsigned short)macKeycode];
+  NSEvent* event = [NSEvent keyEventWithType:type
+                                    location:NSZeroPoint
+                               modifierFlags:flags
+                                   timestamp:TimeIntervalSinceSystemStartup()
+                                windowNumber:[window windowNumber]
+                                     context:nil
+                                  characters:characters
+                 charactersIgnoringModifiers:charactersIgnoringModifiers
+                                   isARepeat:NO
+                                     keyCode:(unsigned short)macKeycode];
 
   return event;
 }