Bug 16420888. Use a ResolutionChangeOrigin for when the resolution is changing...

Bug 16420888. Use a ResolutionChangeOrigin for when the resolution is changing by tests that overides and sets the restore resolution. r=kats

Differential Revision: https://phabricator.services.mozilla.com/D77582

dom/base/nsDOMWindowUtils.cpp

@@ -570,8 +570,7 @@ nsDOMWindowUtils::SetResolutionAndScaleTo(float aResolution) {
     return NS_ERROR_FAILURE;
   }
 
-  presShell->SetResolutionAndScaleTo(aResolution,
-                                     ResolutionChangeOrigin::MainThreadRestore);
+  presShell->SetResolutionAndScaleTo(aResolution, ResolutionChangeOrigin::Test);
 
   return NS_OK;
 }

dom/interfaces/base/nsIDOMWindowUtils.idl

@@ -211,7 +211,8 @@ interface nsIDOMWindowUtils : nsISupports {
                          out uint32_t aHorizontalScrollbarHeight);
 
   /**
-   * Get/set the resolution at which rescalable web content is drawn.
+   * Get/set the resolution at which rescalable web content is drawn for
+   * testing purposes.
    *
    * Setting a new resolution does *not* trigger reflow.  This API is
    * entirely separate from textZoom and fullZoom; a resolution scale
@@ -225,10 +226,13 @@ interface nsIDOMWindowUtils : nsISupports {
    * so that it is displayed at a correspondingly larger or smaller size,
    * without the need for the caller to set an additional transform.
    *
-   * This can be used to implement a non-reflowing scale-zoom, e.g.
-   * for pinch-zoom on mobile platforms.
+   * The purpose of this API is to allow tests to simulate many of the effects
+   * a non-reflowing scale-zoom, e.g. for pinch-zoom on mobile platforms, and
+   * should be only used for testing purposes.
    *
    * The caller of this method must have chrome privileges.
+   *
+   * This is intended to be used by test code only!
    */
   void setResolutionAndScaleTo(in float aResolution);
 

layout/base/MobileViewportManager.cpp

@@ -110,8 +110,9 @@ void MobileViewportManager::ResolutionUpdated(
     return;
   }
 
-  if (!mPainted &&
-      aOrigin == mozilla::ResolutionChangeOrigin::MainThreadRestore) {
+  if ((!mPainted &&
+       aOrigin == mozilla::ResolutionChangeOrigin::MainThreadRestore) ||
+      aOrigin == mozilla::ResolutionChangeOrigin::Test) {
     // Save the value, so our default zoom calculation
     // can take it into account later on.
     SetRestoreResolution(mContext->GetResolution());

layout/base/PresShellForwards.h

@@ -176,6 +176,7 @@ MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(RenderImageFlags)
 
 enum class ResolutionChangeOrigin : uint8_t {
   Apz,
+  Test,
   MainThreadRestore,
   MainThreadAdjustment,
 };