Makes descriptors hold nullptr for properties not implemented in API.

third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl

Index: third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl
diff --git a/third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl b/third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl
index 457060f0e4c2e1601451339999db441ff99cb75c..0cc67d6d5b89221417b0503fc38658112617126a 100644
--- a/third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl
+++ b/third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl
@@ -14,14 +14,21 @@ static_assert(
     "CSSPropertyDescriptor must be a POD to support using initializer lists.");
 
 static CSSPropertyDescriptor cssPropertyDescriptors[] = {
-    // An invalid CSSPropertyDescriptor. When functions are added to
-    // CSSPropertyAPI, add a nullptr to represent their function pointers in the
-    // struct initaliser.
-    { nullptr, false },
-    // When functions are added to CSSPropertyAPI, also add them to the struct
-    // initaliser below.
+    // An invalid CSSPropertyDescriptor.
+    {
+      {% for valid_api_method in valid_api_methods %}
+        nullptr,
+      {% endfor %}
+    },
+    // CSSPropertyDescriptors for all valid properties.
     {% for api_class in api_classes %}
-    { {{api_class.classname}}::parseSingleValue, true },
+    {
+      {% for api_method in api_methods if api_method in api_class.api_methods %}
+      {{api_class.classname}}::{{api_method}},
+      {% else %}
+      nullptr,
+      {% endfor %}
+    },
     {% endfor %}
 };