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// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Copyright (c) 2012, Code Aurora Forum. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/base/request_priority.h"
#include "base/logging.h"
namespace net {
RequestPriority DetermineRequestPriority(ResourceType::Type type)
{
//__android_log_print(ANDROID_LOG_VERBOSE, "Preload", "DetermineRequestPriority, type = %d", type);
// Determine request priority based on how critical this resource typically
// is to user-perceived page load performance. Important considerations are:
// * Can this resource block the download of other resources.
// * Can this resource block the rendering of the page.
// * How useful is the page to the user if this resource is not loaded yet.
switch (type) {
// Main frames are the highest priority because they can block nearly every
// type of other resource and there is no useful display without them.
// Sub frames are a close second, however it is a common pattern to wrap
// ads in an iframe or even in multiple nested iframes. It is worth
// investigating if there is a better priority for them.
case ResourceType::MAIN_FRAME:
case ResourceType::SUB_FRAME:
return HIGHEST;
// Stylesheets and scripts can block rendering and loading of other
// resources. Fonts can block text from rendering.
case ResourceType::STYLESHEET:
case ResourceType::SCRIPT:
case ResourceType::FONT_RESOURCE:
return MEDIUM;
// Sub resources, objects and media are lower priority than potentially
// blocking stylesheets, scripts and fonts, but are higher priority than
// images because if they exist they are probably more central to the page
// focus than images on the page.
case ResourceType::SUB_RESOURCE:
case ResourceType::OBJECT:
case ResourceType::MEDIA:
case ResourceType::WORKER:
case ResourceType::SHARED_WORKER:
return LOW;
// Images are the "lowest" priority because they typically do not block
// downloads or rendering and most pages have some useful content without
// them.
case ResourceType::IMAGE:
return LOWEST;
// Prefetches are at a lower priority than even LOWEST, since they
// are not even required for rendering of the current page.
case ResourceType::PREFETCH:
return IDLE;
default:
// When new resource types are added, their priority must be considered.
NOTREACHED();
return LOW;
}
}
} // namespace net
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