PDF: Change the rotate shortcut keys to ctrl+[] on all platforms.

The default modifier key on Mac is Command, but that conflicts with
the forward and backward keys.

BUG=111232,417902

Review URL: https://codereview.chromium.org/606933002

Cr-Commit-Position: refs/heads/master@{#297033}

chrome/browser/resources/pdf/pdf.js

@@ -235,14 +235,18 @@ PDFViewer.prototype = {
         }
         return;
       case 219:  // left bracket.
+        if (e.ctrlKey) {
           this.plugin_.postMessage({
             type: 'rotateCounterclockwise',
           });
+        }
         return;
       case 221:  // right bracket.
+        if (e.ctrlKey) {
           this.plugin_.postMessage({
             type: 'rotateClockwise',
           });
+        }
         return;
     }
   },

pdf/instance.cc

@@ -587,13 +587,17 @@ bool Instance::HandleInputEvent(const pp::InputEvent& event) {
     }
   }
 
-  if (event.GetType() == PP_INPUTEVENT_TYPE_KEYDOWN &&
-      event.GetModifiers() & kDefaultKeyModifier) {
+  if (event.GetType() == PP_INPUTEVENT_TYPE_KEYDOWN) {
     pp::KeyboardInputEvent keyboard_event(event);
+    const uint32 modifier = event.GetModifiers();
+    if (modifier & kDefaultKeyModifier) {
       switch (keyboard_event.GetKeyCode()) {
         case 'A':
           engine_->SelectAll();
           return true;
+      }
+    } else if (modifier & PP_INPUTEVENT_MODIFIER_CONTROLKEY) {
+      switch (keyboard_event.GetKeyCode()) {
         case ui::VKEY_OEM_4:
           // Left bracket.
           engine_->RotateCounterclockwise();
@@ -604,6 +608,7 @@ bool Instance::HandleInputEvent(const pp::InputEvent& event) {
           return true;
       }
     }
+  }
 
   // Return true for unhandled clicks so the plugin takes focus.
   return (event.GetType() == PP_INPUTEVENT_TYPE_MOUSEDOWN);