Reset pref change registrar when profile is destroyed

Test: tested on Chrome on Linux to verify the crash is gone.
Bug: 1109386
Change-Id: I57761a67b0765d5c0c39e7bafa88a711c5478cc2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2318890
Commit-Queue: Jing Wang <jiwan@chromium.org>
Reviewed-by: Keith Lee <keithlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792555}

chrome/browser/chromeos/input_method/input_method_engine_base.cc

@@ -160,6 +160,7 @@ void InputMethodEngineBase::Initialize(
   profile_ = profile;
 
   if (profile_ && profile->GetPrefs()) {
+    profile_observer_.Add(profile);
     input_method_settings_snapshot_ =
         profile->GetPrefs()
             ->GetDictionary(prefs::kLanguageInputMethodSpecificSettings)
@@ -193,6 +194,14 @@ void InputMethodEngineBase::OnInputMethodOptionsChanged() {
   input_method_settings_snapshot_ = new_settings->Clone();
 }
 
+void InputMethodEngineBase::OnProfileWillBeDestroyed(Profile* profile) {
+  if (profile == profile_) {
+    pref_change_registrar_.reset();
+    profile_observer_.Remove(profile_);
+    profile_ = nullptr;
+  }
+}
+
 void InputMethodEngineBase::FocusIn(
     const ui::IMEEngineHandlerInterface::InputContext& input_context) {
   current_input_type_ = input_context.type;

chrome/browser/chromeos/input_method/input_method_engine_base.h

@@ -10,16 +10,17 @@
 #include <string>
 #include <vector>
 
+#include "base/scoped_observer.h"
 #include "base/time/time.h"
 #include "base/values.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/profiles/profile_observer.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "ui/base/ime/chromeos/input_method_descriptor.h"
 #include "ui/base/ime/composition_text.h"
 #include "ui/base/ime/ime_engine_handler_interface.h"
 #include "url/gurl.h"
 
-class Profile;
-
 namespace ui {
 struct CompositionText;
 class IMEEngineHandlerInterface;
@@ -32,7 +33,8 @@ struct AssistiveWindowButton;
 
 namespace chromeos {
 
-class InputMethodEngineBase : virtual public ui::IMEEngineHandlerInterface {
+class InputMethodEngineBase : virtual public ui::IMEEngineHandlerInterface,
+                              public ProfileObserver {
  public:
   struct KeyboardEvent {
     KeyboardEvent();
@@ -240,11 +242,18 @@ class InputMethodEngineBase : virtual public ui::IMEEngineHandlerInterface {
 
   int GetContextIdForTesting() const { return context_id_; }
 
+  PrefChangeRegistrar* GetPrefChangeRegistrarForTesting() const {
+    return pref_change_registrar_.get();
+  }
+
   // Get the composition bounds.
   const std::vector<gfx::Rect>& composition_bounds() const {
     return composition_bounds_;
   }
 
+  // ProfileObserver:
+  void OnProfileWillBeDestroyed(Profile* profile) override;
+
  protected:
   struct PendingKeyEvent {
     PendingKeyEvent(
@@ -346,6 +355,8 @@ class InputMethodEngineBase : virtual public ui::IMEEngineHandlerInterface {
   std::unique_ptr<PrefChangeRegistrar> pref_change_registrar_;
 
   base::Value input_method_settings_snapshot_;
+
+  ScopedObserver<Profile, ProfileObserver> profile_observer_{this};
 };
 
 }  // namespace chromeos

chrome/browser/chromeos/input_method/native_input_method_engine_browsertest.cc

@@ -594,6 +594,12 @@ IN_PROC_BROWSER_TEST_F(NativeInputMethodEngineTest,
   EXPECT_EQ(observer_->GetChangedEngineId(), "pinyin");
 }
 
+IN_PROC_BROWSER_TEST_F(NativeInputMethodEngineTest, DestroyProfile) {
+  EXPECT_NE(engine_.GetPrefChangeRegistrarForTesting(), nullptr);
+  profile_->MaybeSendDestroyedNotification();
+  EXPECT_EQ(engine_.GetPrefChangeRegistrarForTesting(), nullptr);
+}
+
 class NativeInputMethodEngineAssistiveOff : public InProcessBrowserTest {
  public:
   NativeInputMethodEngineAssistiveOff() {