Bug 1338890 - Cache our tab behaviour instead of requesting it each time on a hot path r=smaug

widget/PuppetWidget.cpp

@@ -76,6 +76,9 @@ MightNeedIMEFocus(const nsWidgetInitData* aInitData)
 // Arbitrary, fungible.
 const size_t PuppetWidget::kMaxDimension = 4000;
 
+static bool gRemoteDesktopBehaviorEnabled = false;
+static bool gRemoteDesktopBehaviorInitialized = false;
+
 NS_IMPL_ISUPPORTS_INHERITED0(PuppetWidget, nsBaseWidget)
 
 PuppetWidget::PuppetWidget(TabChild* aTabChild)
@@ -94,6 +97,11 @@ PuppetWidget::PuppetWidget(TabChild* aTabChild)
 
   // Setting 'Unknown' means "not yet cached".
   mInputContext.mIMEState.mEnabled = IMEState::UNKNOWN;
+
+  if (!gRemoteDesktopBehaviorInitialized) {
+    Preferences::AddBoolVarCache(&gRemoteDesktopBehaviorEnabled, "browser.tabs.remote.desktopbehavior", false);
+    gRemoteDesktopBehaviorInitialized = true;
+  }
 }
 
 PuppetWidget::~PuppetWidget()
@@ -1171,7 +1179,7 @@ PuppetWidget::NeedsPaint()
 {
   // e10s popups are handled by the parent process, so never should be painted here
   if (XRE_IsContentProcess() &&
-      Preferences::GetBool("browser.tabs.remote.desktopbehavior", false) &&
+      gRemoteDesktopBehaviorEnabled &&
       mWindowType == eWindowType_popup) {
     NS_WARNING("Trying to paint an e10s popup in the child process!");
     return false;