Introduce painted-device-scale-factor and use it when --enable-use-zoom-for-dsf is specified.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 6ca3936ddd5a466e8bd50bd772874986276caaf1..dd539337297f4495e1ddef6c6d744a1d2ca197c5 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -38,6 +38,7 @@
 #include "content/child/v8_value_converter_impl.h"
 #include "content/child/webmessageportchannel_impl.h"
 #include "content/common/content_constants_internal.h"
+#include "content/common/content_switches_internal.h"
 #include "content/common/database_messages.h"
 #include "content/common/dom_storage/dom_storage_types.h"
 #include "content/common/drag_messages.h"
@@ -743,8 +744,10 @@ void RenderViewImpl::Initialize(const ViewMsg_New_Params& params,
   // completing initialization.  Otherwise, we can finish it now.
   if (opener_id_ == MSG_ROUTING_NONE)
     did_show_ = true;
-
-  webview()->setDeviceScaleFactor(device_scale_factor_);
+  if (IsUseZoomForDSFEnabled())
+    webview()->setZoomFactorForDeviceScaleFactor(device_scale_factor_);
+  else
+    webview()->setDeviceScaleFactor(device_scale_factor_);
   webview()->setDisplayMode(display_mode_);
   webview()->settings()->setPreferCompositingToLCDTextEnabled(
       PreferCompositingToLCDText(compositor_deps_, device_scale_factor_));
@@ -3183,7 +3186,10 @@ void RenderViewImpl::OnImeConfirmComposition(
 void RenderViewImpl::SetDeviceScaleFactor(float device_scale_factor) {
   RenderWidget::SetDeviceScaleFactor(device_scale_factor);
   if (webview()) {
-    webview()->setDeviceScaleFactor(device_scale_factor);
+    if (IsUseZoomForDSFEnabled())
+      webview()->setZoomFactorForDeviceScaleFactor(device_scale_factor);
+    else
+      webview()->setDeviceScaleFactor(device_scale_factor);
     webview()->settings()->setPreferCompositingToLCDTextEnabled(
         PreferCompositingToLCDText(compositor_deps_, device_scale_factor_));
   }