Don't rewrite events twice.

ui/aura/window_tree_host_unittest.cc

 // Copyright 2016 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 "ui/aura/test/aura_test_base.h"
 #include "ui/aura/test/test_screen.h"
 #include "ui/aura/window.h"
+#include "ui/base/ime/input_method.h"
 #include "ui/compositor/layer.h"
+#include "ui/events/event_rewriter.h"
+
+namespace {
+
+// Counts number of events observed.
+class CounterEventRewriter : public ui::EventRewriter {
+ public:
+  CounterEventRewriter() : events_seen_(0) {}
+  ~CounterEventRewriter() override {}
+
+  int events_seen() const { return events_seen_; }
+
+ private:
+  // ui::EventRewriter:
+  ui::EventRewriteStatus RewriteEvent(
+      const ui::Event& event,
+      std::unique_ptr<ui::Event>* new_event) override {
+    events_seen_++;
+    return ui::EVENT_REWRITE_CONTINUE;
+  }
+
+  ui::EventRewriteStatus NextDispatchEvent(
+      const ui::Event& last_event,
+      std::unique_ptr<ui::Event>* new_event) override {
+    return ui::EVENT_REWRITE_CONTINUE;
+  }
+
+  int events_seen_;
+
+  DISALLOW_COPY_AND_ASSIGN(CounterEventRewriter);
+};
+
+}  // namespace
 
 namespace aura {
 
 using WindowTreeHostTest = test::AuraTestBase;
 
 TEST_F(WindowTreeHostTest, DPIWindowSize) {
   gfx::Rect starting_bounds(0, 0, 800, 600);
   EXPECT_EQ(starting_bounds.size(), host()->compositor()->size());
   EXPECT_EQ(starting_bounds, host()->GetBoundsInPixels());
   EXPECT_EQ(starting_bounds, root_window()->bounds());
@@ skipping 13 matching lines @@
   host()->SetOutputSurfacePaddingInPixels(padding);
   gfx::Rect padded_rect = starting_bounds;
   padded_rect.Inset(-padding);
   EXPECT_EQ(padded_rect.size(), host()->compositor()->size());
   EXPECT_EQ(starting_bounds, host()->GetBoundsInPixels());
   EXPECT_EQ(gfx::Rect(1, 1, 534, 401), root_window()->bounds());
   EXPECT_EQ(gfx::Vector2dF(0, 0),
             host()->compositor()->root_layer()->subpixel_position_offset());
 }
 
+TEST_F(WindowTreeHostTest, NoRewritesPostIME) {
+  CounterEventRewriter event_rewriter;
+  host()->AddEventRewriter(&event_rewriter);
+
+  ui::KeyEvent key_event('A', ui::VKEY_A, 0);
+  host()->GetInputMethod()->DispatchKeyEvent(&key_event);
+  EXPECT_EQ(0, event_rewriter.events_seen());
+
+  host()->RemoveEventRewriter(&event_rewriter);
+}
+
 }  // namespace aura