Remove error handling from MipmapUtil and add DCHECKs

cc/tiles/software_image_decode_controller.cc

 // Copyright 2015 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 "cc/tiles/software_image_decode_controller.h"
 
 #include <inttypes.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 800 matching lines @@
   // If we're going to use the original decode, then the target size should be
   // the full image size, since that will allow for proper memory accounting.
   // Note we skip the decode if the target size is empty altogether, so don't
   // update the target size in that case.
   if (can_use_original_decode && !target_size.IsEmpty())
     target_size = gfx::Size(image.image()->width(), image.image()->height());
 
   if (quality == kMedium_SkFilterQuality && !target_size.IsEmpty()) {
     SkSize mip_target_size =
         MipMapUtil::GetScaleAdjustmentForSize(src_rect.size(), target_size);
-    DCHECK(mip_target_size.width() != -1.f && mip_target_size.height() != -1.f);
     target_size.set_width(src_rect.width() * mip_target_size.width());
     target_size.set_height(src_rect.height() * mip_target_size.height());
   }
 
   return ImageDecodeControllerKey(image.image()->uniqueID(), src_rect,
                                   target_size, quality,
                                   can_use_original_decode);
 }
 
 ImageDecodeControllerKey::ImageDecodeControllerKey(
@@ skipping 140 matching lines @@
 void SoftwareImageDecodeController::MemoryBudget::ResetUsage() {
   current_usage_bytes_ = 0;
 }
 
 size_t SoftwareImageDecodeController::MemoryBudget::GetCurrentUsageSafe()
     const {
   return current_usage_bytes_.ValueOrDie();
 }
 
 }  // namespace cc