Decouple VR Shell DPR and CSS size from Physical Displays.

chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.cc

Index: chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.cc
diff --git a/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.cc b/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.cc
index 7eb33f110f6836998ec784e8f325605d9862e22a..100dbab45acf05d2ccade950cd1a9a13890b9e5d 100644
--- a/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.cc
+++ b/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.cc
@@ -35,6 +35,9 @@ void VrShellUIMessageHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "doAction", base::Bind(&VrShellUIMessageHandler::HandleDoAction,
                              base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
+      "setCssSize", base::Bind(&VrShellUIMessageHandler::HandleSetCssSize,
+                               base::Unretained(this)));
 }
 
 void VrShellUIMessageHandler::HandleDomLoaded(const base::ListValue* args) {
@@ -72,6 +75,17 @@ void VrShellUIMessageHandler::HandleDoAction(const base::ListValue* args) {
   }
 }
 
+void VrShellUIMessageHandler::HandleSetCssSize(const base::ListValue* args) {
+  CHECK(args->GetSize() == 3);
+  double width, height, dpr;
+  CHECK(args->GetDouble(0, &width));

[cjgrant, 2016/11/29 20:28:06]

Might be clearer to pass a dictionary of 'width', 'height', 'dpr', in the first
list item, and drop the length check.  Just a thought.

[mthiesse, 2016/11/29 21:07:21]

Length check is equivalent to checking a dictionary is present at all. If you
prefer passing named values I can change it, but for a call this simple I don't
think it matters.

+  CHECK(args->GetDouble(1, &height));
+  CHECK(args->GetDouble(2, &dpr));
+  if (vr_shell_) {
+    vr_shell_->SetUiCssSize(width, height, dpr);

[cjgrant, 2016/11/29 20:28:06]

Does this not need to be synchronized on the rendering thread?

[mthiesse, 2016/11/29 21:07:21]

Yes and No. This part does not, it has to be called on the UI thread. The
callback VrShell::UiBoundsChanged should really be synchronized with the
rendering thread, but that's not so simple and I was planning on addressing it
in a followup patch. The problem is we don't know when the renderer actually
gives us a frame with the new size, which might be any number of frames in the
future. Right now we draw some small number of incorrect frames when changing
size. I'll throw a TODO in VrShell::UiBoundsChanged for now.

+  }
+}
+
 void VrShellUIMessageHandler::SendCommandToUi(const base::Value& value) {
   CallJavascriptFunction("vrShellUi.command", value);
 }