From ba1afc2fcfc466fecb93ac77f91d46b72785d6bb Mon Sep 17 00:00:00 2001
From: Arthur Edelstein <arthuredelstein@gmail.com>
Date: Wed, 23 Sep 2015 10:20:44 -0700
Subject: [PATCH] Bug 17009: Pref to suppress some modifier key events

---
 layout/base/nsIPresShell.h  |  3 +++
 layout/base/nsPresShell.cpp | 15 +++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/layout/base/nsIPresShell.h b/layout/base/nsIPresShell.h
index cbbae0e8fd22e..dc0bb0ab40503 100644
--- a/layout/base/nsIPresShell.h
+++ b/layout/base/nsIPresShell.h
@@ -1861,6 +1861,9 @@ protected:
   // to true, so we can avoid any paint calls for widget related to this
   // presshell.
   bool mIsNeverPainting;
+
+  // If true, don't report Alt, Shift, and AltGr KeyboardEvents to content.
+  static bool sSuppressModifierKeyEvents;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIPresShell, NS_IPRESSHELL_IID)
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 56ac370b96d1f..1db07f8e54c4a 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -242,6 +242,8 @@ static nsClassHashtable<nsUint32HashKey,
 static nsClassHashtable<nsUint32HashKey,
                         nsIPresShell::PointerInfo>* sActivePointersIds;
 
+bool nsIPresShell::sSuppressModifierKeyEvents = false;
+
 // RangePaintInfo is used to paint ranges to offscreen buffers
 struct RangePaintInfo {
   RefPtr<nsRange> mRange;
@@ -7174,6 +7176,16 @@ PresShell::HandleKeyboardEvent(nsINode* aTarget,
                                nsEventStatus* aStatus,
                                EventDispatchingCallback* aEventCB)
 {
+  if (nsContentUtils::ResistFingerprinting() && sSuppressModifierKeyEvents) {
+    nsString keyName;
+    aEvent.GetDOMKeyName(keyName);
+    if (keyName.Equals(NS_LITERAL_STRING("Shift")) ||
+        keyName.Equals(NS_LITERAL_STRING("Alt")) ||
+        keyName.Equals(NS_LITERAL_STRING("AltGraph"))) {
+      aEvent.mFlags.mOnlyChromeDispatch = true;
+    }
+  }
+
   MOZ_ASSERT(aTarget);
   
   // return true if the event target is in its child process
@@ -10913,6 +10925,9 @@ void nsIPresShell::InitializeStatics()
   sPointerCaptureList =
     new nsClassHashtable<nsUint32HashKey, PointerCaptureInfo>;
   sActivePointersIds = new nsClassHashtable<nsUint32HashKey, PointerInfo>;
+  Preferences::AddBoolVarCache(&sSuppressModifierKeyEvents,
+                               "privacy.suppressModifierKeyEvents", false);
+
 }
 
 void nsIPresShell::ReleaseStatics()
-- 
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