Measure the usage of cross-origin modal dialogs.

third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp

Index: third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
index 20a01b9f6b24d98edfe157a16ae76c19f7f7615c..a956131d01253adcebf09c72beb48f7f2fbd9329 100644
--- a/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
@@ -764,6 +764,10 @@ void LocalDOMWindow::print(ScriptState* scriptState)
         m_shouldPrintWhenFinishedLoading = true;
         return;
     }
+
+    if (frame()->isCrossOrigin()) {

[dcheng, 2016/06/21 11:20:02]

Nit: no { } around a single-line conditional body

+        UseCounter::count(frame()->document(), UseCounter::CrossOriginWindowPrint);
+    }
     m_shouldPrintWhenFinishedLoading = false;
     host->chromeClient().print(frame());
 }
@@ -802,6 +806,10 @@ void LocalDOMWindow::alert(ScriptState* scriptState, const String& message)
     if (!host)
         return;
 
+    if (frame()->isCrossOrigin()) {
+        UseCounter::count(frame()->document(), UseCounter::CrossOriginWindowAlert);
+    }
+
     host->chromeClient().openJavaScriptAlert(frame(), message);
 }
 
@@ -832,6 +840,9 @@ bool LocalDOMWindow::confirm(ScriptState* scriptState, const String& message)
     if (!host)
         return false;
 
+    if (frame()->isCrossOrigin()) {
+        UseCounter::count(frame()->document(), UseCounter::CrossOriginWindowConfirm);
+    }
     return host->chromeClient().openJavaScriptConfirm(frame(), message);
 }
 
@@ -866,6 +877,10 @@ String LocalDOMWindow::prompt(ScriptState* scriptState, const String& message, c
     if (host->chromeClient().openJavaScriptPrompt(frame(), message, defaultValue, returnValue))
         return returnValue;
 
+    if (frame()->isCrossOrigin()) {
+        UseCounter::count(frame()->document(), UseCounter::CrossOriginWindowPrompt);
+    }
+
     return String();
 }