Bug 1583575: Retain window size between instances and use it to set the size when opening a new window; r=snorp

This obviously only improves the situation when a subsequent window is the
same size as the last window that was opened.

Differential Revision: https://phabricator.services.mozilla.com/D50527

--HG--
extra : moz-landing-system : lando

widget/android/nsWindow.cpp

@@ -131,6 +131,18 @@ static const int32_t INPUT_RESULT_HANDLED =
 static const int32_t INPUT_RESULT_HANDLED_CONTENT =
     java::PanZoomController::INPUT_RESULT_HANDLED_CONTENT;
 
+/**
+ * Width and height from the last nsWindow::Resize call, used for setting
+ * dimensions of a new window under the heuristic that a new window is likely
+ * to be the same size as a previous window.
+ *
+ * A default size of 1x1 confuses MobileViewportManager, so we use 0x0 instead.
+ * This is also a little more fitting since we don't yet have a surface yet
+ * (and therefore a valid size) and 0x0 is usually recognized as invalid.
+ */
+static int32_t gLastWidth = 0;
+static int32_t gLastHeight = 0;
+
 template <typename Lambda, bool IsStatic, typename InstanceType, class Impl>
 class nsWindow::WindowEvent : public Runnable {
   bool IsStaleCall() {
@@ -1498,11 +1510,7 @@ nsresult nsWindow::Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
     mParent = parent;
   }
 
-  // A default size of 1x1 confuses MobileViewportManager, so
-  // use 0x0 instead. This is also a little more fitting since
-  // we don't yet have a surface yet (and therefore a valid size)
-  // and 0x0 is usually recognized as invalid.
-  Resize(0, 0, false);
+  Resize(gLastWidth, gLastHeight, false);
 
   CreateLayerManager();
 
@@ -1702,8 +1710,8 @@ void nsWindow::Resize(double aX, double aY, double aWidth, double aHeight,
 
   mBounds.x = NSToIntRound(aX);
   mBounds.y = NSToIntRound(aY);
-  mBounds.width = NSToIntRound(aWidth);
-  mBounds.height = NSToIntRound(aHeight);
+  mBounds.width = gLastWidth = NSToIntRound(aWidth);
+  mBounds.height = gLastHeight = NSToIntRound(aHeight);
 
   if (needSizeDispatch) {
     OnSizeChanged(gfx::IntSize::Truncate(aWidth, aHeight));