Raise the loading priority of in-viewport images.

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
new file mode 100644
index 0000000000000000000000000000000000000000..483f2eb21582f8e2e4f9c156f02dc04b58cdf0d7
--- /dev/null
+++ b/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "core/fetch/ResourceLoadPriorityOptimizer.h"
+
+namespace WebCore {
+
+ResourceLoadPriorityOptimizer::ResourceAndVisibility::ResourceAndVisibility(ImageResource* img, bool v)
+    : imageResource(img)
+    , visible(v)
+{
+}
+
+ResourceLoadPriorityOptimizer::ResourceAndVisibility::ResourceAndVisibility()

[eseidel, 2013/11/25 23:59:30]

Shoud this just have one constructor and have it have 2 args with default
values?

[shatch, 2013/11/26 01:35:18]

Both std::map and HashMap seem to want a default constructor to create empty
elements. Alternatively, I could just new each instance of ResourceAndVisibility
to get around this. wdyt?

+    : imageResource(0)
+    , visible(false)
+{
+}
+
+ResourceLoadPriorityOptimizer::ResourceAndVisibility::ResourceAndVisibility(const ResourceLoadPriorityOptimizer::ResourceAndVisibility& o)

[eseidel, 2013/11/25 23:59:30]

Again, my C++ is a bit weak here.  How is this different from the default copy
constructor?

[shatch, 2013/11/26 01:35:18]

Yeah I think you're right, it's not any different, removing this.

+    : imageResource(o.imageResource)
+    , visible(o.visible)
+{
+}
+
+ResourceLoadPriorityOptimizer::ResourceAndVisibility::~ResourceAndVisibility()
+{
+}
+
+ResourceLoadPriorityOptimizer::ResourceLoadPriorityOptimizer()
+{
+}
+
+ResourceLoadPriorityOptimizer::~ResourceLoadPriorityOptimizer()
+{
+    updateImageResourcesWithLoadPriority();
+}
+
+void ResourceLoadPriorityOptimizer::updateImageResourcesWithLoadPriority()
+{
+    for (ImageResourceMap::iterator it = m_imageResources.begin(); it != m_imageResources.end(); ++it) {
+        ResourceLoadPriority priority = it->second.visible ? ResourceLoadPriorityLow : ResourceLoadPriorityVeryLow;
+        it->second.imageResource->didChangePriority(priority);
+    }
+    m_imageResources.clear();
+}
+
+void ResourceLoadPriorityOptimizer::notifyImageResourceVisibility(ImageResource* img, bool visible)
+{
+    if (!img || img->isLoaded())
+        return;
+
+    if (visible) {
+        m_imageResources[img->identifier()] = ResourceAndVisibility(img, visible);
+    } else {
+        // If the resource exists in the map, don't overwrite since it might have been visible from
+        // some other RenderObject.
+        if (m_imageResources.find(img->identifier()) == m_imageResources.end())

[eseidel, 2013/11/25 23:59:30]

I'm surprised this doesn't have a .contains()?  I guess thsi is std::map?

[shatch, 2013/11/26 01:35:18]

Yeah it was a std::map, don't believe it has a contains() function. Changed this
to HashMap per other comment anyway.

+            m_imageResources[img->identifier()] = ResourceAndVisibility(img, visible);
+    }
+}
+
+}