Implements a display scale tray setting behind a chrome switch

ui/display/display.cc

Index: ui/display/display.cc
diff --git a/ui/display/display.cc b/ui/display/display.cc
index 25573f8f9b90e3408ab9234162a0a9b0c92aae70..c403905fb597c5a9201bbce2b6f2b1807c67c725 100644
--- a/ui/display/display.cc
+++ b/ui/display/display.cc
@@ -90,6 +90,16 @@ void Display::ResetForceDeviceScaleFactorForTesting() {
   g_forced_device_scale_factor = -1.0;
 }
 
+// static
+void Display::SetForceDeviceScaleFactor(double dsf) {
+  // Reset any previously set values and unset the flag.
+  g_has_forced_device_scale_factor = -1;
+  g_forced_device_scale_factor = -1.0;

[oshima, 2017/05/09 03:58:21]

I somehow missed this change in the first review.

Just setting g_forced_device_scale_factor, g_has_forced_device_scale_factor
didn't work?

[malaykeshav, 2017/05/10 05:28:27]

It should work. I just read the comment for `g_has_forced_device_scale_factor`: 
"This variable tracks whether the forced device scale factor switch needs to be
read from the command line" which was misleading.

+
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kForceDeviceScaleFactor, base::StringPrintf("%.2f", dsf));
+}
+
 Display::Display() : Display(kInvalidDisplayId) {}
 
 Display::Display(int64_t id) : Display(id, gfx::Rect()) {}