media: Fix CdmAdapter member variable declaration order

Move |cdm_| to the bottom of the declaration list so that it is
destructed first when CdmAdapter is destructed. This would help prevent
|cdm_| from accessing other deleted member during destruction.

Also clean up the declaration of other members to map initialization
order.

BUG=510088

Change-Id: I7c8535c503226089db1d7fd3ce6afcd22bc38dce
Reviewed-on: https://chromium-review.googlesource.com/742327Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512620}

media/cdm/cdm_adapter.cc

@@ -447,8 +447,6 @@ CdmAdapter::CdmAdapter(
       session_closed_cb_(session_closed_cb),
       session_keys_change_cb_(session_keys_change_cb),
       session_expiration_update_cb_(session_expiration_update_cb),
-      audio_samples_per_second_(0),
-      audio_channel_layout_(CHANNEL_LAYOUT_NONE),
       helper_(std::move(helper)),
       task_runner_(base::ThreadTaskRunnerHandle::Get()),
       pool_(new AudioBufferMemoryPool()),

media/cdm/cdm_adapter.h

@@ -204,12 +204,8 @@ class MEDIA_EXPORT CdmAdapter : public ContentDecryptionModule,
                                 uint32_t link_mask,
                                 uint32_t protection_mask);
 
-  // Used to keep track of promises while the CDM is processing the request.
-  CdmPromiseAdapter cdm_promise_adapter_;
-
-  std::unique_ptr<CdmWrapper> cdm_;
-  std::string key_system_;
-  CdmConfig cdm_config_;
+  const std::string key_system_;
+  const CdmConfig cdm_config_;
 
   // Callbacks for firing session events.
   SessionMessageCB session_message_cb_;
@@ -217,6 +213,12 @@ class MEDIA_EXPORT CdmAdapter : public ContentDecryptionModule,
   SessionKeysChangeCB session_keys_change_cb_;
   SessionExpirationUpdateCB session_expiration_update_cb_;
 
+  // Helper that provides additional functionality for the CDM.
+  std::unique_ptr<CdmAuxiliaryHelper> helper_;
+
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_refptr<AudioBufferMemoryPool> pool_;
+
   // Callbacks for deferred initialization.
   DecoderInitCB audio_init_cb_;
   DecoderInitCB video_init_cb_;
@@ -225,20 +227,20 @@ class MEDIA_EXPORT CdmAdapter : public ContentDecryptionModule,
   NewKeyCB new_audio_key_cb_;
   NewKeyCB new_video_key_cb_;
 
+  // Keep track of audio parameters.
+  int audio_samples_per_second_ = 0;
+  ChannelLayout audio_channel_layout_ = CHANNEL_LAYOUT_NONE;
+
   // Keep track of video frame natural size from the latest configuration
   // as the CDM doesn't provide it.
   gfx::Size natural_size_;
 
-  // Keep track of audio parameters.
-  int audio_samples_per_second_;
-  ChannelLayout audio_channel_layout_;
-
-  // Helper that provides additional functionality for the CDM.
-  std::unique_ptr<CdmAuxiliaryHelper> helper_;
-
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  // Used to keep track of promises while the CDM is processing the request.
+  CdmPromiseAdapter cdm_promise_adapter_;
 
-  scoped_refptr<AudioBufferMemoryPool> pool_;
+  // Declare |cdm_| after other member variables to avoid the CDM accessing
+  // deleted objects (e.g. |helper_|) during destruction.
+  std::unique_ptr<CdmWrapper> cdm_;
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<CdmAdapter> weak_factory_;