Add metrics for dialogs triggered inside sandboxed documents.

Source/core/frame/LocalDOMWindow.cpp

Index: Source/core/frame/LocalDOMWindow.cpp
diff --git a/Source/core/frame/LocalDOMWindow.cpp b/Source/core/frame/LocalDOMWindow.cpp
index 910d97e89ed762cbde1ef975296265d49a815018..6934f4b2610fa44618642dbf6680c2ade8beae9f 100644
--- a/Source/core/frame/LocalDOMWindow.cpp
+++ b/Source/core/frame/LocalDOMWindow.cpp
@@ -825,6 +825,9 @@ void LocalDOMWindow::print()
     }
     m_shouldPrintWhenFinishedLoading = false;
     host->chrome().print(frame());
+
+    if (frame()->document()->sandboxFlags())
+        UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
 }
 
 void LocalDOMWindow::stop()
@@ -845,6 +848,9 @@ void LocalDOMWindow::alert(const String& message)
     if (!host)
         return;
 
+    if (frame()->document()->sandboxFlags())
+        UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
+
     host->chrome().runJavaScriptAlert(frame(), message);
 }
 
@@ -859,6 +865,9 @@ bool LocalDOMWindow::confirm(const String& message)
     if (!host)
         return false;
 
+    if (frame()->document()->sandboxFlags())
+        UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
+
     return host->chrome().runJavaScriptConfirm(frame(), message);
 }
 
@@ -873,6 +882,9 @@ String LocalDOMWindow::prompt(const String& message, const String& defaultValue)
     if (!host)
         return String();
 
+    if (frame()->document()->sandboxFlags())
+        UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
+
     String returnValue;
     if (host->chrome().runJavaScriptPrompt(frame(), message, defaultValue, returnValue))
         return returnValue;