[Slimming Paint] Implement deferred SVG filters

Source/core/rendering/svg/SVGRenderingContext.cpp

Index: Source/core/rendering/svg/SVGRenderingContext.cpp
diff --git a/Source/core/rendering/svg/SVGRenderingContext.cpp b/Source/core/rendering/svg/SVGRenderingContext.cpp
index fade7cdbfc7ac74d9b8230b186e54624e8465a31..03931939eebf6a4683037af246d0d81ba4ef1150 100644
--- a/Source/core/rendering/svg/SVGRenderingContext.cpp
+++ b/Source/core/rendering/svg/SVGRenderingContext.cpp
@@ -34,6 +34,8 @@
 #include "core/rendering/svg/SVGResources.h"
 #include "core/rendering/svg/SVGResourcesCache.h"
 #include "platform/FloatConversion.h"
+#include "platform/graphics/paint/DrawingRecorder.h"
+#include "third_party/skia/include/core/SkPicture.h"
 
 namespace blink {
 
@@ -42,7 +44,11 @@ SVGRenderingContext::~SVGRenderingContext()
     if (m_filter) {
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object));
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object)->filter() == m_filter);
-        m_filter->finishEffect(m_object, m_paintInfo.context);
+        DrawingRecorder recorder(m_originalPaintInfo->context, m_object->displayItemClient(), DisplayItem::SVGFilter, LayoutRect::infiniteRect());
+        m_filter->finishEffect(m_object, m_originalPaintInfo->context, m_paintInfo.context);
+
+        // Reset the main context after the filter effect has been completed.
+        m_paintInfo.context = m_originalPaintInfo->context;
     }
 
     if (m_masker) {
@@ -149,10 +155,22 @@ bool SVGRenderingContext::applyFilterIfNecessary(SVGResources* resources)
         if (m_object->style()->svgStyle().hasFilter())
             return false;
     } else if (RenderSVGResourceFilter* filter = resources->filter()) {
-        if (!filter->prepareEffect(m_object, m_paintInfo.context))
+        if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+            m_filterContentDisplayItemList = DisplayItemList::create();
+            m_filterContentGraphicsContext = adoptPtr(new GraphicsContext(nullptr, m_filterContentDisplayItemList.get()));
+        }
+
+        // Instead of drawing into the regular context, we draw into a (sometimes separate)
+        // context just for the contents of the filter.
+        GraphicsContext* filterContents = m_filterContentGraphicsContext ? m_filterContentGraphicsContext.get() : m_paintInfo.context;

[chrishtr, 2015/01/24 00:02:02]

Declare filterContents before line 158 and init to m_paintInfo.context, then
override it after line 160. This avoids two conditionals that always trigger on
the same conditions.

Also, do you mean filterContext, not filterContents?

[pdr., 2015/01/24 01:13:36]

Done. Refactored this even further and removed the filterConte(nt/xt).

+        if (!filter->prepareEffect(m_object, filterContents))
             return false;
+
         m_filter = filter;
 
+        if (m_filterContentGraphicsContext)
+            m_paintInfo.context = m_filterContentGraphicsContext.get();
+
         // Because we cache the filter contents and do not invalidate on paint
         // invalidation rect changes, we need to paint the entire filter region
         // so elements outside the initial paint (due to scrolling, etc) paint.