Do not block painting for in-body CSS

third_party/WebKit/Source/core/dom/ProcessingInstruction.cpp

Index: third_party/WebKit/Source/core/dom/ProcessingInstruction.cpp
diff --git a/third_party/WebKit/Source/core/dom/ProcessingInstruction.cpp b/third_party/WebKit/Source/core/dom/ProcessingInstruction.cpp
index 4338ba519334f6b51f9c0c83cec16402bfec78c1..da02b2704b07b5b3d46bb1670055df337ba31137 100644
--- a/third_party/WebKit/Source/core/dom/ProcessingInstruction.cpp
+++ b/third_party/WebKit/Source/core/dom/ProcessingInstruction.cpp
@@ -41,6 +41,7 @@ inline ProcessingInstruction::ProcessingInstruction(Document& document, const St
     : CharacterData(document, data, CreateOther)
     , m_target(target)
     , m_loading(false)
+    , m_beforeBody(false)
     , m_alternate(false)
     , m_isCSS(false)
     , m_isXSL(false)
@@ -165,8 +166,10 @@ void ProcessingInstruction::process(const String& href, const String& charset)
 
     if (resource) {
         m_loading = true;
-        if (!m_isXSL)
-            document().styleEngine().addPendingSheet();
+        if (!m_isXSL) {
+            m_beforeBody = m_beforeBody || !document().body();
+            document().styleEngine().addPendingSheet(m_beforeBody);
+        }
         setResource(resource);
     }
 }
@@ -184,7 +187,7 @@ bool ProcessingInstruction::sheetLoaded()
 {
     if (!isLoading()) {
         if (!DocumentXSLT::sheetLoaded(document(), this))
-            document().styleEngine().removePendingSheet(this);
+            document().styleEngine().removePendingSheet(this, m_beforeBody);
         return true;
     }
     return false;
@@ -288,7 +291,7 @@ void ProcessingInstruction::clearSheet()
 {
     DCHECK(m_sheet);
     if (m_sheet->isLoading())
-        document().styleEngine().removePendingSheet(this);
+        document().styleEngine().removePendingSheet(this, m_beforeBody);
     m_sheet.release()->clearOwnerNode();
 }