Fix two bugs found by a new clang warning I'm currently testing:

media/video/capture/fake_video_capture_device.cc

 // Copyright (c) 2011 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 "media/video/capture/fake_video_capture_device.h"
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/stringprintf.h"
@@ skipping 52 matching lines @@
   if (width > 320) {  // VGA
     current_settings.width = 640;
     current_settings.height = 480;
     current_settings.frame_rate = 30;
   } else {  // QVGA
     current_settings.width = 320;
     current_settings.height = 240;
     current_settings.frame_rate = 30;
   }
 
-  fake_frame_.reset(new uint8[current_settings.width *
-                              current_settings.height * 3 / 2]);
-  memset(fake_frame_.get(), 0, sizeof(fake_frame_.get()));
+  size_t fake_frame_size =
+      current_settings.width * current_settings.height * 3 / 2;
+  fake_frame_.reset(new uint8[fake_frame_size]);
+  memset(fake_frame_.get(), 0, fake_frame_size);
 
   state_ = kAllocated;
   observer_->OnFrameInfo(current_settings);
 }
 
 void FakeVideoCaptureDevice::Start() {
   if (state_ != kAllocated) {
       return;  // Wrong state.
   }
   state_ = kCapturing;
@@ skipping 32 matching lines @@
                                      sizeof(fake_frame_.get()),
                                      base::Time::Now());
   // Reschedule next CaptureTask.
   capture_thread_.message_loop()->PostDelayedTask(
         FROM_HERE,
         NewRunnableMethod(this, &FakeVideoCaptureDevice::OnCaptureTask),
         kFakeCaptureTimeoutMs);
 }
 
 }  // namespace media