Add support for virtual displays

ui/display/chromeos/display_snapshot_virtual.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/display/chromeos/display_snapshot_virtual.h"
+
+#include <inttypes.h>
+
+#include "base/strings/stringprintf.h"
+#include "ui/display/types/display_mode.h"
+
+namespace ui {
+DisplaySnapshotVirtual::DisplaySnapshotVirtual(int64_t display_id,
+                                               gfx::Size display_size)
+    : DisplaySnapshot(display_id,
+                      gfx::Point(0, 0),
+                      // TODO(robert.bradford): Use better physical dimensions.
+                      gfx::Size(200, 200),

[oshima, 2015/11/24 22:19:27]

why not display_size ?

[robert.bradford, 2015/11/26 16:29:40]

This parameter is for the physical size. I've replaced it with dimensions for a
non-hidpi display.

[oshima, 2015/12/02 20:34:27]

I think this will be used to compute the DPI threshold to determine device scale
factor.
Will the physical size be available through cast API?

For now, please add comment that this is picked to use lower dsf.

[robert.bradford, 2015/12/03 18:44:57]

Or, as i've just posted, calculate the physical display based on 96dpi. How does
that sound?

[oshima, 2015/12/03 18:54:07]

sgtm

+                      DISPLAY_CONNECTION_TYPE_VIRTUAL,
+                      false,
+                      false,
+                      "Virtual display",
+                      std::vector<const DisplayMode*>(),
+                      NULL,
+                      NULL) {
+  mode_.reset(new DisplayMode(display_size, false, 30));
+  modes_.push_back(mode_.get());
+
+  native_mode_ = modes_.front();
+}
+
+DisplaySnapshotVirtual::~DisplaySnapshotVirtual() {}
+
+std::string DisplaySnapshotVirtual::ToString() const {
+  return base::StringPrintf(
+      "Virtual id=%" PRId64 " current_mode=%s physical_size=%s", display_id_,
+      current_mode_ ? current_mode_->ToString().c_str() : "NULL",
+      physical_size_.ToString().c_str());
+}
+
+}  // namespace ui