Make sure string passed to sendMessageToEmbedder is a valid unicode string

The message passed to the method is a result of JSON.stringify and may contain noncharacter unicode code points (http://www.unicode.org/faq/private_use.html#noncharacters). Since we know that the message is a JSON string we can use \uXXXX escape sequences for bad symbols. The function escapes not only noncharacters which produces valid output and allows to keep implementation simple.

BUG=347899
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/178473027

git-svn-id: svn://svn.chromium.org/blink/trunk@168448 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/inspector/InspectorFrontendHost.cpp

@@ -160,16 +160,33 @@ void InspectorFrontendHost::copyText(const String& text)
     Pasteboard::generalPasteboard()->writePlainText(text, Pasteboard::CannotSmartReplace);
 }
 
+static String escapeUnicodeNonCharacters(const String& str)
+{
+    StringBuilder dst;
+    for (unsigned i = 0; i < str.length(); ++i) {
+        UChar c = str[i];
+        if (c > 126) {
+            unsigned symbol = static_cast<unsigned>(c);
+            String symbolCode = String::format("\\u%04X", symbol);
+            dst.append(symbolCode);
+        } else {
+            dst.append(c);
+        }
+
+    }
+    return dst.toString();
+}
+
 void InspectorFrontendHost::sendMessageToBackend(const String& message)
 {
     if (m_client)
-        m_client->sendMessageToBackend(message);
+        m_client->sendMessageToBackend(escapeUnicodeNonCharacters(message));
 }
 
 void InspectorFrontendHost::sendMessageToEmbedder(const String& message)
 {
     if (m_client)
-        m_client->sendMessageToEmbedder(message);
+        m_client->sendMessageToEmbedder(escapeUnicodeNonCharacters(message));
 }
 
 void InspectorFrontendHost::showContextMenu(Event* event, const Vector<ContextMenuItem>& items)