InputMethodEngine's cached composition text should be cleared when re…

…set & CommitText.

BUG=522782
TEST=Verified the bug not repro on local sandbox.

Review URL: https://codereview.chromium.org/1307783003

Cr-Commit-Position: refs/heads/master@{#345554}
(cherry picked from commit 952eb74)

Review URL: https://codereview.chromium.org/1320573004 .

Cr-Commit-Position: refs/branch-heads/2490@{#196}
Cr-Branched-From: 7790a35-refs/heads/master@{#344925}

chrome/browser/chromeos/input_method/input_method_engine.cc

@@ -275,6 +275,7 @@ bool InputMethodEngine::CommitText(int context_id, const char* text,
     size_t len = GetUtf8StringLength(text);
     UMA_HISTOGRAM_CUSTOM_COUNTS("InputMethod.CommitLength",
                                 len, 1, 25, 25);
+    composition_text_.reset(new CompositionText());
   }
   return true;
 }
@@ -613,6 +614,7 @@ void InputMethodEngine::PropertyActivate(const std::string& property_name) {
 void InputMethodEngine::Reset() {
   if (!CheckProfile())
     return;
+  composition_text_.reset(new CompositionText());
   observer_->OnReset(active_component_id_);
 }
 

chrome/browser/chromeos/input_method/input_method_engine_unittest.cc

@@ -240,15 +240,17 @@ TEST_F(InputMethodEngineTest, TestHistograms) {
   FocusIn(ui::TEXT_INPUT_TYPE_TEXT);
   engine_->Enable(kTestImeComponentId);
   std::vector<InputMethodEngineInterface::SegmentInfo> segments;
-  engine_->SetComposition(
-      engine_->GetCotextIdForTesting(), "test", 0, 0, 0, segments, NULL);
+  int context = engine_->GetCotextIdForTesting();
   std::string error;
   base::HistogramTester histograms;
-  engine_->CommitText(1, "input", &error);
-  engine_->CommitText(1,
+  engine_->SetComposition(context, "test", 0, 0, 0, segments, NULL);
+  engine_->CommitText(context, "input", &error);
+  engine_->SetComposition(context, "test", 0, 0, 0, segments, NULL);
+  engine_->CommitText(context,
                       "\xE5\x85\xA5\xE5\x8A\x9B",  // 2 UTF-8 characters
                       &error);
-  engine_->CommitText(1, "input\xE5\x85\xA5\xE5\x8A\x9B", &error);
+  engine_->SetComposition(context, "test", 0, 0, 0, segments, NULL);
+  engine_->CommitText(context, "input\xE5\x85\xA5\xE5\x8A\x9B", &error);
   histograms.ExpectTotalCount("InputMethod.CommitLength", 3);
   histograms.ExpectBucketCount("InputMethod.CommitLength", 5, 1);
   histograms.ExpectBucketCount("InputMethod.CommitLength", 2, 1);