Adds a test for setting empty composition text.

ui/base/ime/dummy_text_input_client.cc

Index: ui/base/ime/dummy_text_input_client.cc
diff --git a/ui/base/ime/dummy_text_input_client.cc b/ui/base/ime/dummy_text_input_client.cc
index 60ae481d1271b00dbbf923076471778687ea565e..91c3b3b10c160cb81659162edd1eb2464e737d39 100644
--- a/ui/base/ime/dummy_text_input_client.cc
+++ b/ui/base/ime/dummy_text_input_client.cc
@@ -9,35 +9,28 @@
 namespace ui {
 
 DummyTextInputClient::DummyTextInputClient()
-    : text_input_type_(TEXT_INPUT_TYPE_NONE),
-      insert_char_count_(0),
-      insert_text_count_(0),
-      set_composition_count_(0) {}
+    : text_input_type_(TEXT_INPUT_TYPE_NONE), insert_char_count_(0) {}
 
 DummyTextInputClient::DummyTextInputClient(TextInputType text_input_type)
-    : text_input_type_(text_input_type),
-      insert_char_count_(0),
-      insert_text_count_(0),
-      set_composition_count_(0) {}
+    : text_input_type_(text_input_type), insert_char_count_(0) {}
 
 DummyTextInputClient::~DummyTextInputClient() {
 }
 
 void DummyTextInputClient::SetCompositionText(
     const CompositionText& composition) {
-  ++set_composition_count_;
-  last_composition_.CopyFrom(composition);
+  composition_history_.push_back(composition);
 }
 
 void DummyTextInputClient::ConfirmCompositionText() {
 }
 
 void DummyTextInputClient::ClearCompositionText() {
+  SetCompositionText(CompositionText());
 }
 
 void DummyTextInputClient::InsertText(const base::string16& text) {
-  ++insert_text_count_;
-  last_insert_text_ = text;
+  insert_text_history_.push_back(text);
 }
 
 void DummyTextInputClient::InsertChar(const KeyEvent& event) {