Fix Resource Priorities and Scheduling (Blink Side)

Source/core/fetch/ResourceLoadPriorityOptimizer.cpp

Index: Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
diff --git a/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp b/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
index 721386ed1f684e72d47d52ed423ce3482c1c7656..b200b7a171fc2aa60e2a6563c0766b848b9bea1d 100644
--- a/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
+++ b/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
@@ -30,6 +30,7 @@
 
 #include "config.h"
 #include "core/fetch/ResourceLoadPriorityOptimizer.h"
+#include "core/frame/Settings.h"
 #include "core/layout/LayoutObject.h"
 #include "platform/TraceEvent.h"
 
@@ -55,6 +56,8 @@ ResourceLoadPriorityOptimizer::ResourceAndVisibility::~ResourceAndVisibility()
 }
 
 ResourceLoadPriorityOptimizer::ResourceLoadPriorityOptimizer()
+    : m_retrievedSettings(false)
+    , m_increaseFetchPriorities(false)
 {
 }
 
@@ -64,6 +67,10 @@ ResourceLoadPriorityOptimizer::~ResourceLoadPriorityOptimizer()
 
 void ResourceLoadPriorityOptimizer::addLayoutObject(LayoutObject* layoutObject)
 {
+    if (!m_retrievedSettings) {

[Bryan McQuade, 2015/08/07 17:30:40]

it's kind of unfortunate that we have to do this here, in addLayoutObject, in
order to save some state that's needed in a different method. I see that this is
the only place that we really have access to a settings object though.

Maybe instead we could change the updateAllImageResourcePriorities method, which
is the only method that calls updateImageResourcesWithLoadPriority, to take a
Settings object (or a Document, or whatever you think is appropriate)? There are
only 2 call sites to updateAllImageResourcePriorities. Both are in FrameView
which should be able to easily look up a Settings object.

[Pat Meenan, 2015/08/07 21:21:14]

We could but passing around the document or settings object doesn't feel that
much cleaner on the surface.  I'm assuming the code is only going to live for
the duration of the field trial and then we can just rip it out entirely.

+        m_increaseFetchPriorities = layoutObject->document().settings()->fetchIncreasePriorities();
+        m_retrievedSettings = true;
+    }
     m_objects.add(layoutObject);
     layoutObject->setHasPendingResourceUpdate(true);
 }
@@ -98,6 +105,11 @@ void ResourceLoadPriorityOptimizer::updateImageResourcesWithLoadPriority()
         ResourceLoadPriority priority = resource.value->status == Visible ?
             ResourceLoadPriorityLow : ResourceLoadPriorityVeryLow;
 
+        if (m_increaseFetchPriorities) {
+            priority = resource.value->status == Visible ?
+                ResourceLoadPriorityHigh : ResourceLoadPriorityLow;
+        }
+
         if (priority != resource.value->imageResource->resourceRequest().priority()) {
             resource.value->imageResource->mutableResourceRequest().setPriority(priority, resource.value->screenArea);
             resource.value->imageResource->didChangePriority(priority, resource.value->screenArea);