Bug 1634703 - Add a parent-process-only method to nsIDOMWindowUtils to get the native window ID from a window. r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D73481

dom/base/nsDOMWindowUtils.cpp

@@ -4342,3 +4342,26 @@ nsDOMWindowUtils::GetPaintCount(uint64_t* aPaintCount) {
   *aPaintCount = presShell ? presShell->GetPaintCount() : 0;
   return NS_OK;
 }
+
+NS_IMETHODIMP
+nsDOMWindowUtils::GetWebrtcRawDeviceId(nsAString& aRawDeviceId) {
+  if (!XRE_IsParentProcess()) {
+    MOZ_CRASH(
+        "GetWebrtcRawDeviceId is only available in the parent "
+        "process");
+  }
+
+  nsIWidget* widget = GetWidget();
+  if (!widget) {
+    return NS_ERROR_FAILURE;
+  }
+
+  int64_t rawDeviceId =
+      (int64_t)(widget->GetNativeData(NS_NATIVE_WINDOW_WEBRTC_DEVICE_ID));
+  if (!rawDeviceId) {
+    return NS_ERROR_FAILURE;
+  }
+
+  aRawDeviceId.AppendInt(rawDeviceId);
+  return NS_OK;
+}

dom/interfaces/base/nsIDOMWindowUtils.idl

@@ -2054,6 +2054,15 @@ interface nsIDOMWindowUtils : nsISupports {
 
   // Returns true if we are using overlay scrollbars.
   readonly attribute bool usesOverlayScrollbars;
+
+  // Returns the ID for the underlying window widget, which can
+  // be compared against the rawId from a nsIMediaDevice to determine
+  // if the window is being shared.
+  //
+  // Using this only makes sense in the parent process, and the function
+  // will intentionally crash any non-parent process that tries to access
+  // it.
+  readonly attribute AString webrtcRawDeviceId;
 };
 
 [scriptable, uuid(c694e359-7227-4392-a138-33c0cc1f15a6)]

widget/nsIWidget.h

@@ -131,6 +131,7 @@ typedef void* nsNativeWidget;
 // IME context.  Note that the result is only valid in the process.  So,
 // XP code should use nsIWidget::GetNativeIMEContext() instead of using this.
 #define NS_RAW_NATIVE_IME_CONTEXT 14
+#define NS_NATIVE_WINDOW_WEBRTC_DEVICE_ID 15
 #ifdef XP_MACOSX
 #  define NS_NATIVE_PLUGIN_PORT_QD 100
 #  define NS_NATIVE_PLUGIN_PORT_CG 101