Cross-process frames should be notified of device scale factor changes.

content/browser/site_per_process_browsertest.cc

Index: content/browser/site_per_process_browsertest.cc
diff --git a/content/browser/site_per_process_browsertest.cc b/content/browser/site_per_process_browsertest.cc
index 82125646ac4fa50758b58fafa5da3c3cb5029ab3..eefbcae6451cce2ebed2bb51431fcc3494113433 100644
--- a/content/browser/site_per_process_browsertest.cc
+++ b/content/browser/site_per_process_browsertest.cc
@@ -61,6 +61,7 @@
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "third_party/WebKit/public/web/WebSandboxFlags.h"
 #include "ui/display/display_switches.h"
+#include "ui/display/screen.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
 #include "ui/gfx/geometry/point.h"
@@ -589,13 +590,16 @@ void SitePerProcessBrowserTest::SetUpOnMainThread() {
 
 class SitePerProcessHighDPIBrowserTest : public SitePerProcessBrowserTest {
  public:
+  const double kDeviceScaleFactor = 2.0;
+
   SitePerProcessHighDPIBrowserTest() {}
 
  protected:
   void SetUpCommandLine(base::CommandLine* command_line) override {
     SitePerProcessBrowserTest::SetUpCommandLine(command_line);
-    command_line->AppendSwitchASCII(switches::kForceDeviceScaleFactor,
-                                    base::StringPrintf("2"));
+    command_line->AppendSwitchASCII(
+        switches::kForceDeviceScaleFactor,
+        base::StringPrintf("%f", kDeviceScaleFactor));
   }
 };
 
@@ -613,6 +617,93 @@ class SitePerProcessIgnoreCertErrorsBrowserTest
   }
 };
 
+double GetFrameDeviceScaleFactor(const ToRenderFrameHost& adapter) {
+  double device_scale_factor;
+  const char kGetFrameDeviceScaleFactor[] =
+      "window.domAutomationController.send(window.devicePixelRatio);";
+  EXPECT_TRUE(ExecuteScriptAndExtractDouble(adapter, kGetFrameDeviceScaleFactor,
+                                            &device_scale_factor));
+  return device_scale_factor;
+}
+
+IN_PROC_BROWSER_TEST_F(SitePerProcessHighDPIBrowserTest,
+                       SubframeLoadsWithCorrectDeviceScaleFactor) {
+  GURL main_url(embedded_test_server()->GetURL(
+      "a.com", "/cross_site_iframe_factory.html?a(b)"));
+  NavigateToURL(shell(), main_url);
+
+  EXPECT_EQ(SitePerProcessHighDPIBrowserTest::kDeviceScaleFactor,
+            GetFrameDeviceScaleFactor(web_contents()));
+
+  FrameTreeNode* root = web_contents()->GetFrameTree()->root();
+  FrameTreeNode* child = root->child_at(0);
+  EXPECT_EQ(SitePerProcessHighDPIBrowserTest::kDeviceScaleFactor,
+            GetFrameDeviceScaleFactor(child));
+}
+
+class DisplayMetricsChangedObserver : public display::DisplayObserver {
+ public:
+  DisplayMetricsChangedObserver(uint32_t metrics_flags)
+      : metrics_flags_(metrics_flags), device_scale_factor_changed_(false) {}
+
+  void OnDisplayAdded(const display::Display&) override {}
+  void OnDisplayRemoved(const display::Display&) override {}
+
+  void OnDisplayMetricsChanged(const display::Display& display,
+                               uint32_t changed_metrics) override {
+    if ((changed_metrics & metrics_flags_) == metrics_flags_) {
+      device_scale_factor_changed_ = true;
+
+      if (!message_loop_runner_)
+        return;
+
+      message_loop_runner_->Quit();
+    }
+  }
+
+  void WaitForDeviceScaleFactorChanged() {
+    if (device_scale_factor_changed_)
+      return;
+
+    message_loop_runner_ = new MessageLoopRunner;
+    message_loop_runner_->Run();
+  }
+
+ private:
+  uint32_t metrics_flags_;
+  bool device_scale_factor_changed_;
+  scoped_refptr<MessageLoopRunner> message_loop_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(DisplayMetricsChangedObserver);
+};
+
+IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest,
+                       DeviceScaleFactorChangePropagatesToAllFrames) {
+  GURL main_url(embedded_test_server()->GetURL(
+      "a.com", "/cross_site_iframe_factory.html?a(b)"));
+  NavigateToURL(shell(), main_url);
+
+  EXPECT_EQ(1.0, GetFrameDeviceScaleFactor(web_contents()));
+
+  FrameTreeNode* root = web_contents()->GetFrameTree()->root();
+  FrameTreeNode* child = root->child_at(0);
+  EXPECT_EQ(1.0, GetFrameDeviceScaleFactor(child));
+
+  display::Screen* screen = display::Screen::GetScreen();
+
+  float new_device_scale_factor = 2.5f;
+  {
+    DisplayMetricsChangedObserver observer(
+        display::DisplayObserver::DISPLAY_METRIC_DEVICE_SCALE_FACTOR);
+    screen->AddObserver(&observer);
+    screen->SetDeviceScaleFactorForTest(new_device_scale_factor);
+    observer.WaitForDeviceScaleFactorChanged();
+    screen->RemoveObserver(&observer);
+  }
+  EXPECT_EQ(new_device_scale_factor, GetFrameDeviceScaleFactor(web_contents()));
+  EXPECT_EQ(new_device_scale_factor, GetFrameDeviceScaleFactor(child));
+}
+
 // Ensure that navigating subframes in --site-per-process mode works and the
 // correct documents are committed.
 #if defined(OS_WIN)