Add a few missing overrides found by a new clang warning.

Namely, -Winconsistent-missing-override. No behavior change.

BUG=428099

Review URL: https://codereview.chromium.org/687693004

Cr-Commit-Position: refs/heads/master@{#301746}

diff --git a/ipc/ipc_channel.h b/ipc/ipc_channel.h
index f077def..2fc52cb5 100644
--- a/ipc/ipc_channel.h
+++ b/ipc/ipc_channel.h

@@ -173,11 +173,12 @@
   // Get its own process id. This value is told to the peer.
   virtual base::ProcessId GetSelfPID() const = 0;
 
+  // Overridden from ipc::Sender.
   // Send a message over the Channel to the listener on the other end.
   //
   // |message| must be allocated using operator new.  This object will be
   // deleted once the contents of the Message have been sent.
-  virtual bool Send(Message* message) = 0;
+  virtual bool Send(Message* message) override = 0;
 
   // NaCl in Non-SFI mode runs on Linux directly, and the following functions
   // compiled on Linux are also needed. Please see also comments in

diff --git a/ipc/ipc_channel_win.h b/ipc/ipc_channel_win.h
index 2f9fee2a..7a2d484 100644
--- a/ipc/ipc_channel_win.h
+++ b/ipc/ipc_channel_win.h

@@ -61,7 +61,7 @@
   // MessageLoop::IOHandler implementation.
   virtual void OnIOCompleted(base::MessageLoopForIO::IOContext* context,
                              DWORD bytes_transfered,
-                             DWORD error);
+                             DWORD error) override;
 
  private:
   struct State {

diff --git a/sandbox/win/src/sandbox_policy_base.h b/sandbox/win/src/sandbox_policy_base.h
index aac4d65c..b1c17dc 100644
--- a/sandbox/win/src/sandbox_policy_base.h
+++ b/sandbox/win/src/sandbox_policy_base.h

@@ -66,7 +66,7 @@
   virtual ResultCode SetStderrHandle(HANDLE handle) override;
   virtual ResultCode AddRule(SubSystem subsystem, Semantics semantics,
                              const wchar_t* pattern) override;
-  virtual ResultCode AddDllToUnload(const wchar_t* dll_name);
+  virtual ResultCode AddDllToUnload(const wchar_t* dll_name) override;
   virtual ResultCode AddKernelObjectToClose(
       const base::char16* handle_type,
       const base::char16* handle_name) override;

diff --git a/ui/gfx/animation/animation.h b/ui/gfx/animation/animation.h
index 81e8e2b..9f152d17 100644
--- a/ui/gfx/animation/animation.h
+++ b/ui/gfx/animation/animation.h

@@ -82,7 +82,7 @@
 
   // AnimationContainer::Element overrides
   void SetStartTime(base::TimeTicks start_time) override;
-  virtual void Step(base::TimeTicks time_now) = 0;
+  virtual void Step(base::TimeTicks time_now) override = 0;
   base::TimeDelta GetTimerInterval() const override;
 
  private: