Bug 958596 - Add a Describe() method to nsIContent. r=bz

content/base/public/Element.h

@@ -492,6 +492,8 @@ public:
   void ListAttributes(FILE* out) const;
 #endif
 
+  void Describe(nsAString& aOutDescription) const MOZ_OVERRIDE;
+
   /*
    * Attribute Mapping Helpers
    */
@@ -514,6 +516,8 @@ public:
   }
 
 private:
+  void DescribeAttribute(uint32_t index, nsAString& aOutDescription) const;
+
   static bool
   FindAttributeDependence(const nsIAtom* aAttribute,
                           const MappedAttributeEntry* const aMaps[],

content/base/public/nsIContent.h

@@ -950,6 +950,15 @@ public:
                            bool aDumpAll = true) const = 0;
 #endif
 
+  /**
+   * Append to aOutDescription a short (preferably one line) string
+   * describing the content.
+   * Currently implemented for elements only.
+   */
+  virtual void Describe(nsAString& aOutDescription) const {
+    aOutDescription = NS_LITERAL_STRING("(not an element)");
+  }
+
   enum ETabFocusType {
   //eTabFocus_textControlsMask = (1<<0),  // unused - textboxes always tabbable
     eTabFocus_formElementsMask = (1<<1),  // non-text form elements

content/base/src/Element.cpp

@@ -2132,30 +2132,35 @@ Element::GetAttrCount() const
   return mAttrsAndChildren.AttrCount();
 }
 
+void
+Element::DescribeAttribute(uint32_t index, nsAString& aOutDescription) const
+{
+  // name
+  mAttrsAndChildren.AttrNameAt(index)->GetQualifiedName(aOutDescription);
+
+  // value
+  aOutDescription.AppendLiteral("=\"");
+  nsAutoString value;
+  mAttrsAndChildren.AttrAt(index)->ToString(value);
+  for (int i = value.Length(); i >= 0; --i) {
+    if (value[i] == char16_t('"'))
+      value.Insert(char16_t('\\'), uint32_t(i));
+  }
+  aOutDescription.Append(value);
+  aOutDescription.AppendLiteral("\"");
+}
+
 #ifdef DEBUG
 void
 Element::ListAttributes(FILE* out) const
 {
   uint32_t index, count = mAttrsAndChildren.AttrCount();
   for (index = 0; index < count; index++) {
-    nsAutoString buffer;
-
-    // name
-    mAttrsAndChildren.AttrNameAt(index)->GetQualifiedName(buffer);
-
-    // value
-    buffer.AppendLiteral("=\"");
-    nsAutoString value;
-    mAttrsAndChildren.AttrAt(index)->ToString(value);
-    for (int i = value.Length(); i >= 0; --i) {
-      if (value[i] == char16_t('"'))
-        value.Insert(char16_t('\\'), uint32_t(i));
-    }
-    buffer.Append(value);
-    buffer.AppendLiteral("\"");
+    nsAutoString attributeDescription;
+    DescribeAttribute(index, attributeDescription);
 
     fputs(" ", out);
-    fputs(NS_LossyConvertUTF16toASCII(buffer).get(), out);
+    fputs(NS_LossyConvertUTF16toASCII(attributeDescription).get(), out);
   }
 }
 
@@ -2279,6 +2284,21 @@ Element::DumpContent(FILE* out, int32_t aIndent,
 }
 #endif
 
+void
+Element::Describe(nsAString& aOutDescription) const
+{
+  aOutDescription.Append(mNodeInfo->QualifiedName());
+  aOutDescription.AppendPrintf("@%p", (void *)this);
+
+  uint32_t index, count = mAttrsAndChildren.AttrCount();
+  for (index = 0; index < count; index++) {
+    aOutDescription.Append(' ');
+    nsAutoString attributeDescription;
+    DescribeAttribute(index, attributeDescription);
+    aOutDescription.Append(attributeDescription);
+  }
+}
+
 bool
 Element::CheckHandleEventForLinksPrecondition(nsEventChainVisitor& aVisitor,
                                               nsIURI** aURI) const