Add instance counters of Resource and AudioNode, and expose them via WebLeakDetector.

Source/core/fetch/Resource.cpp

Index: Source/core/fetch/Resource.cpp
diff --git a/Source/core/fetch/Resource.cpp b/Source/core/fetch/Resource.cpp
index 8e0389e6bd3e42b08d098641316bbac90870e101..ff898e2a129f2decc402aee403328c16bf45330b 100644
--- a/Source/core/fetch/Resource.cpp
+++ b/Source/core/fetch/Resource.cpp
@@ -93,6 +93,7 @@ static inline bool shouldUpdateHeaderAfterRevalidation(const AtomicString& heade
 }
 
 DEFINE_DEBUG_ONLY_GLOBAL(RefCountedLeakCounter, cachedResourceLeakCounter, ("Resource"));
+unsigned Resource::s_instanceCount = 0;
 
 Resource::Resource(const ResourceRequest& request, Type type)
     : m_resourceRequest(request)
@@ -120,6 +121,7 @@ Resource::Resource(const ResourceRequest& request, Type type)
     , m_proxyResource(nullptr)
 {
     ASSERT(m_type == unsigned(type)); // m_type is a bitfield, so this tests careless updates of the enum.
+    ++s_instanceCount;
 #ifndef NDEBUG
     cachedResourceLeakCounter.increment();
 #endif
@@ -149,6 +151,7 @@ Resource::~Resource()
 #ifndef NDEBUG
     cachedResourceLeakCounter.decrement();
 #endif
+    --s_instanceCount;
 }
 
 void Resource::dispose()