Don't rewrite events twice.

ui/aura/window_tree_host_unittest.cc

Index: ui/aura/window_tree_host_unittest.cc
diff --git a/ui/aura/window_tree_host_unittest.cc b/ui/aura/window_tree_host_unittest.cc
index e4ce37c0412da271e98a48a6b44d8d4d5cd9c894..7da3eb9853d1e149186189ff4e4b8485c5f4ba99 100644
--- a/ui/aura/window_tree_host_unittest.cc
+++ b/ui/aura/window_tree_host_unittest.cc
@@ -5,7 +5,41 @@
 #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 {
 
@@ -39,4 +73,15 @@ TEST_F(WindowTreeHostTest, DPIWindowSize) {
             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