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_test_proxy.h"
 #include "gin/arguments.h"
 #include "gin/handle.h"
@@ skipping 239 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
   key_down.setKeyIdentifierFromWindowsKeyCode();
   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.

[yabinh, 2016/06/17 06:15:10]

Some test will fail because of this bug, like:

https://cs.corp.google.com/clankium/src/third_party/WebKit/LayoutTests/editin...

It didn't fail before because we used to do boundary control in
inputMethodController. So even though it returned an larger length, and exceeded
the right boundary, it could still work. But now we do boundary control in
render_widget, so the bug shows up.

By the way, there is no such bug in ImeTest, because we use std::string16.

+  blink::WebString newText = blink::WebString::fromUTF8(text);
+  size_t textLength = base::string16(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_test_proxy_base_->web_view();
 }
 
 }  // namespace test_runner