Bug 1154125 - Ensure the context has up-to-date device pixel DPI scaling before using it in calling nsViewManager::SetWindowDimensions. r=mstange

--HG--
extra : rebase_source : c757bbeae9b86e139b32c224c6df01318cc7a33f

layout/base/nsDocumentViewer.cpp

@@ -1919,6 +1919,14 @@ nsDocumentViewer::SetBoundsWithFlags(const nsIntRect& aBounds, uint32_t aFlags)
                     aBounds.width, aBounds.height,
                     false);
   } else if (mPresContext && mViewManager) {
+    // Ensure presContext's deviceContext is up to date, as we sometimes get
+    // here before a resolution-change notification has been fully handled
+    // during display configuration changes, especially when there are lots
+    // of windows/widgets competing to handle the notifications.
+    // (See bug 1154125.)
+    if (mPresContext->DeviceContext()->CheckDPIChange()) {
+      mPresContext->UIResolutionChanged();
+    }
     int32_t p2a = mPresContext->AppUnitsPerDevPixel();
     mViewManager->SetWindowDimensions(NSIntPixelsToAppUnits(mBounds.width, p2a),
                                       NSIntPixelsToAppUnits(mBounds.height, p2a),