DevTools: remove unused parts of the CSS instrumentation.

Source/core/css/CSSStyleSheet.cpp

Index: Source/core/css/CSSStyleSheet.cpp
diff --git a/Source/core/css/CSSStyleSheet.cpp b/Source/core/css/CSSStyleSheet.cpp
index ab1f3d21ee8ad0776dcbfcdd5a0968afb541f520..f4ceccaa9341adc36ab1caf1545b55212efc58a4 100644
--- a/Source/core/css/CSSStyleSheet.cpp
+++ b/Source/core/css/CSSStyleSheet.cpp
@@ -162,8 +162,6 @@ CSSStyleSheet::~CSSStyleSheet()
 
 void CSSStyleSheet::willMutateRules()
 {
-    InspectorInstrumentation::willMutateRules(this);
-
     // If we are the only client it is safe to mutate.
     if (m_contents->clientSize() <= 1 && !m_contents->isInMemoryCache()) {
         m_contents->clearRuleSet();
@@ -191,7 +189,6 @@ void CSSStyleSheet::didMutateRules()
     ASSERT(m_contents->isMutable());
     ASSERT(m_contents->clientSize() <= 1);
 
-    InspectorInstrumentation::didMutateRules(this);
     didMutate(PartialRuleUpdate);
 }