Reset scroll and scale while toggling "Request desktop site"

third_party/WebKit/Source/core/loader/FrameLoader.cpp

Index: third_party/WebKit/Source/core/loader/FrameLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/FrameLoader.cpp b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
index 88a37090d94e7a300e77612224a34c69260eede3..1b6492b2c31aefcf2ac1a872c454ff793dbc7432 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
@@ -1105,6 +1105,10 @@ void FrameLoader::RestoreScrollPositionAndViewStateForLoadType(
   bool should_restore_scroll =
       history_item->ScrollRestorationType() != kScrollRestorationManual;
   bool should_restore_scale = history_item->PageScaleFactor();
+  if (!frame_->GetSettings()->GetViewportMetaEnabled()) {

[aelias_OOO_until_Jul13, 2017/05/25 02:56:08]

Unfortunately, there are indeed side effects:
1. On other Chrome platforms this setting is always false, because viewport meta
is mobile-specific feature.  So this is universally disabling scroll/scale
restore on non-Android.
2. Even if this were wrapped in "#if OS(ANDROID)" (which is discouraged pattern
anyway), we will also see the problem that further navigations starting from the
desktop site will no longer restore scroll/scale properly.

So this needs to be done conditionally that the *last* navigation was a special
RDS reload.

[jaebaek, 2017/05/25 04:10:34]

Does it mean that I must add a parameter which let the system know the reload is
actually from RDS and set it as TRUE at the moment when
NavigationControllerAndroid::SetUseDesktopUserAgent() is called (i.e., RDS
button is clicked)?

In the case, the parameter definitely will sent to settings (e.g., we can get it
by calling frame_->GetSettings()->GetRDSEnabled() here).

+    should_restore_scroll = false;
+    should_restore_scale = false;
+  }
 
   // This tries to balance:
   // 1. restoring as soon as possible