Implement chrome.input.ime.setComposition/commitText API.

chrome/browser/ui/input_method/input_method_engine_base.cc

Index: chrome/browser/ui/input_method/input_method_engine_base.cc
diff --git a/chrome/browser/ui/input_method/input_method_engine_base.cc b/chrome/browser/ui/input_method/input_method_engine_base.cc
index 6cd3a6412a8490e8e9f83855ee09d7d0cd56556d..5377dfa9e37e29e46ee8b11ad6748bed14c49c45 100644
--- a/chrome/browser/ui/input_method/input_method_engine_base.cc
+++ b/chrome/browser/ui/input_method/input_method_engine_base.cc
@@ -249,6 +249,13 @@ bool InputMethodEngineBase::SetComposition(
     composition_text_->underlines.push_back(underline);
   }
 
+  // Use a black thin underline by default.
+  if (composition_text_->underlines.empty()) {
+    composition_text_->underlines.push_back(ui::CompositionUnderline(
+        0, composition_text_->text.length(), SK_ColorBLACK, false /* thick */,
+        SK_ColorTRANSPARENT));
+  }
+
   // TODO(nona): Makes focus out mode configuable, if necessary.
   UpdateComposition(*composition_text_, composition_cursor_, true);
   return true;