Reland: Fix setComposingText with empty text when newCursorPosition != 1

components/test_runner/text_input_controller.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/test_runner/text_input_controller.h"
 
 #include "base/macros.h"
 #include "components/test_runner/web_view_test_proxy.h"
 #include "gin/arguments.h"
 #include "gin/handle.h"
@@ skipping 265 matching lines @@
 
 void TextInputController::SetComposition(const std::string& text) {
   // Sends a keydown event with key code = 0xE5 to emulate input method
   // behavior.
   blink::WebKeyboardEvent key_down;
   key_down.type = blink::WebInputEvent::RawKeyDown;
   key_down.modifiers = 0;
   key_down.windowsKeyCode = 0xE5;  // VKEY_PROCESSKEY
   view()->handleInputEvent(key_down);
 
+  // The value returned by std::string::length() may not correspond to the
+  // actual number of encoded characters in sequences of multi-byte or
+  // variable-length characters.
+  blink::WebString newText = blink::WebString::fromUTF8(text);
+  size_t textLength = newText.length();
+
   std::vector<blink::WebCompositionUnderline> underlines;
-  underlines.push_back(blink::WebCompositionUnderline(0, text.length(),
-                                                      SK_ColorBLACK, false,
-                                                      SK_ColorTRANSPARENT));
+  underlines.push_back(blink::WebCompositionUnderline(
+      0, textLength, SK_ColorBLACK, false, SK_ColorTRANSPARENT));
   view()->setComposition(
-      blink::WebString::fromUTF8(text),
-      blink::WebVector<blink::WebCompositionUnderline>(underlines),
-      text.length(), text.length());
+      newText, blink::WebVector<blink::WebCompositionUnderline>(underlines),
+      textLength, textLength);
 }
 
 blink::WebView* TextInputController::view() {
   return web_view_test_proxy_base_->web_view();
 }
 
 }  // namespace test_runner