Add console messages when modals are suppressed due to sandboxing.

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 951255ace8577aa40c02952f5350e1c789f533be..2842e4b38ebbd988b33af2c22f5cad5b712fe9ab 100644
--- a/Source/core/frame/LocalDOMWindow.cpp
+++ b/Source/core/frame/LocalDOMWindow.cpp
@@ -787,8 +787,10 @@ void LocalDOMWindow::print()
 
     if (frame()->document()->isSandboxed(SandboxModals)) {
         UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
-        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled())
+        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled()) {
+            frameConsole()->addMessage(ConsoleMessage::create(SecurityMessageSource, ErrorMessageLevel, "Ignored call to 'print()'. The document is sandboxed, and the 'allow-modals' keyword is not set."));
             return;
+        }
     }
 
     if (frame()->isLoading()) {
@@ -813,8 +815,10 @@ void LocalDOMWindow::alert(const String& message)
 
     if (frame()->document()->isSandboxed(SandboxModals)) {
         UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
-        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled())
+        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled()) {
+            frameConsole()->addMessage(ConsoleMessage::create(SecurityMessageSource, ErrorMessageLevel, "Ignored call to 'alert()'. The document is sandboxed, and the 'allow-modals' keyword is not set."));
             return;
+        }
     }
 
     frame()->document()->updateLayoutTreeIfNeeded();
@@ -833,8 +837,10 @@ bool LocalDOMWindow::confirm(const String& message)
 
     if (frame()->document()->isSandboxed(SandboxModals)) {
         UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
-        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled())
+        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled()) {
+            frameConsole()->addMessage(ConsoleMessage::create(SecurityMessageSource, ErrorMessageLevel, "Ignored call to 'confirm()'. The document is sandboxed, and the 'allow-modals' keyword is not set."));
             return false;
+        }
     }
 
     frame()->document()->updateLayoutTreeIfNeeded();
@@ -843,12 +849,6 @@ bool LocalDOMWindow::confirm(const String& message)
     if (!host)
         return false;
 
-    if (frame()->document()->isSandboxed(SandboxModals)) {
-        UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
-        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled())
-            return false;
-    }
-
     return host->chromeClient().openJavaScriptConfirm(frame(), message);
 }
 
@@ -859,8 +859,10 @@ String LocalDOMWindow::prompt(const String& message, const String& defaultValue)
 
     if (frame()->document()->isSandboxed(SandboxModals)) {
         UseCounter::count(frame()->document(), UseCounter::DialogInSandboxedContext);
-        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled())
+        if (RuntimeEnabledFeatures::sandboxBlocksModalsEnabled()) {
+            frameConsole()->addMessage(ConsoleMessage::create(SecurityMessageSource, ErrorMessageLevel, "Ignored call to 'prompt()'. The document is sandboxed, and the 'allow-modals' keyword is not set."));
             return String();
+        }
     }
 
     frame()->document()->updateLayoutTreeIfNeeded();