Bug 1374875 - Use simpler mutation observer than nsRange for media elements. r=cpearce

MozReview-Commit-ID: FVPdHC6tBXg

dom/html/HTMLMediaElement.cpp

@@ -1403,7 +1403,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(HTMLMediaElement, nsGenericHTM
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSrcMediaSource)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSrcStream)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSrcAttrStream)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSourcePointer)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mLoadBlockedDoc)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSourceLoadCandidate)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAudioChannelWrapper)
@@ -1422,6 +1421,7 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(HTMLMediaElement, nsGenericHTM
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLMediaElement, nsGenericHTMLElement)
+  tmp->RemoveMutationObserver(tmp);
   if (tmp->mSrcStream) {
     // Need to EndMediaStreamPlayback to clear mSrcStream and make sure everything
     // gets unhooked correctly.
@@ -1430,7 +1430,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLMediaElement, nsGenericHTMLE
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSrcAttrStream)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mMediaSource)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSrcMediaSource)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSourcePointer)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mLoadBlockedDoc)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSourceLoadCandidate)
   if (tmp->mAudioChannelWrapper) {
@@ -1463,6 +1462,35 @@ NS_IMPL_BOOL_ATTR(HTMLMediaElement, Loop, loop)
 NS_IMPL_BOOL_ATTR(HTMLMediaElement, DefaultMuted, muted)
 NS_IMPL_ENUM_ATTR_DEFAULT_VALUE(HTMLMediaElement, Preload, preload, nullptr)
 
+void
+HTMLMediaElement::ContentInserted(nsIDocument* aDocument,
+                                  nsIContent*  aContainer,
+                                  nsIContent*  aChild,
+                                  int32_t      aIndexInContainer)
+{
+  if (aContainer != this ||
+      aIndexInContainer >= int32_t(mSourcePointer) ||
+      aIndexInContainer < 0) {
+    return;
+  }
+  ++mSourcePointer;
+}
+
+void
+HTMLMediaElement::ContentRemoved(nsIDocument* aDocument,
+                                 nsIContent*  aContainer,
+                                 nsIContent*  aChild,
+                                 int32_t      aIndexInContainer,
+                                 nsIContent*  aPreviousSibling)
+{
+  if (aContainer != this ||
+      aIndexInContainer >= int32_t(mSourcePointer) ||
+      aIndexInContainer < 0) {
+    return;
+  }
+  --mSourcePointer;
+}
+
 NS_IMETHODIMP_(bool)
 HTMLMediaElement::IsVideo()
 {
@@ -1741,7 +1769,7 @@ void HTMLMediaElement::AbortExistingLoads()
   mIsEncrypted = false;
   mPendingEncryptedInitData.Reset();
   mWaitingForKey = NOT_WAITING_FOR_KEY;
-  mSourcePointer = nullptr;
+  mSourcePointer = 0;
 
   mTags = nullptr;
 
@@ -2249,6 +2277,8 @@ void HTMLMediaElement::LoadFromSourceChildren()
     parentDoc->FlushPendingNotifications(FlushType::Layout);
   }
 
+  AddMutationObserverUnlessExists(this);
+
   while (true) {
     nsIContent* child = GetNextSource();
     if (!child) {
@@ -3708,6 +3738,7 @@ HTMLMediaElement::HTMLMediaElement(already_AddRefed<mozilla::dom::NodeInfo>& aNo
     mSrcStreamPausedCurrentTime(-1),
     mShutdownObserver(new ShutdownObserver),
     mCurrentLoadID(0),
+    mSourcePointer(0),
     mNetworkState(nsIDOMHTMLMediaElement::NETWORK_EMPTY),
     mReadyState(nsIDOMHTMLMediaElement::HAVE_NOTHING, "HTMLMediaElement::mReadyState"),
     mLoadWaitStatus(NOT_WAITING),
@@ -6356,46 +6387,16 @@ void HTMLMediaElement::NotifyAddedSource()
 
 nsIContent* HTMLMediaElement::GetNextSource()
 {
-  nsCOMPtr<nsIDOMNode> thisDomNode = do_QueryObject(this);
-
   mSourceLoadCandidate = nullptr;
 
-  nsresult rv = NS_OK;
-  if (!mSourcePointer) {
-    // First time this has been run, create a selection to cover children.
-    mSourcePointer = new nsRange(this);
-    // If this media element is removed from the DOM, don't gravitate the
-    // range up to its ancestor, leave it attached to the media element.
-    mSourcePointer->SetEnableGravitationOnElementRemoval(false);
-
-    rv = mSourcePointer->SelectNodeContents(thisDomNode);
-    if (NS_FAILED(rv)) return nullptr;
-
-    rv = mSourcePointer->Collapse(true);
-    if (NS_FAILED(rv)) return nullptr;
-  }
-
   while (true) {
-#ifdef DEBUG
-    nsCOMPtr<nsIDOMNode> startContainer;
-    rv = mSourcePointer->GetStartContainer(getter_AddRefs(startContainer));
-    if (NS_FAILED(rv)) return nullptr;
-    NS_ASSERTION(startContainer == thisDomNode,
-                "Should only iterate over direct children");
-#endif
-
-    int32_t startOffset = 0;
-    rv = mSourcePointer->GetStartOffset(&startOffset);
-    NS_ENSURE_SUCCESS(rv, nullptr);
-
-    if (uint32_t(startOffset) == GetChildCount())
+    if (mSourcePointer >= GetChildCount())
       return nullptr; // No more children.
 
-    // Advance the range to the next child.
-    rv = mSourcePointer->SetStart(thisDomNode, startOffset + 1);
-    NS_ENSURE_SUCCESS(rv, nullptr);
+    nsIContent* child = GetChildAt(mSourcePointer);
 
-    nsIContent* child = GetChildAt(startOffset);
+    // Advance to the next child.
+    ++mSourcePointer;
 
     // If child is a <source> element, it is the next candidate.
     if (child && child->IsHTMLElement(nsGkAtoms::source)) {

dom/html/HTMLMediaElement.h

@@ -23,6 +23,7 @@
 #include "mozilla/StateWatching.h"
 #include "nsGkAtoms.h"
 #include "PrincipalChangeObserver.h"
+#include "nsStubMutationObserver.h"
 
 // X.h on Linux #defines CurrentTime as 0L, so we have to #undef it here.
 #ifdef CurrentTime
@@ -84,7 +85,8 @@ class HTMLMediaElement : public nsGenericHTMLElement,
                          public nsIDOMHTMLMediaElement,
                          public MediaDecoderOwner,
                          public PrincipalChangeObserver<DOMMediaStream>,
-                         public SupportsWeakPtr<HTMLMediaElement>
+                         public SupportsWeakPtr<HTMLMediaElement>,
+                         public nsStubMutationObserver
 {
 public:
   typedef mozilla::TimeStamp TimeStamp;
@@ -96,6 +98,8 @@ public:
   typedef mozilla::MetadataTags MetadataTags;
 
   MOZ_DECLARE_WEAKREFERENCE_TYPENAME(HTMLMediaElement)
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
 
   CORSMode GetCORSMode() {
     return mCORSMode;
@@ -1378,8 +1382,10 @@ protected:
   uint32_t mCurrentLoadID;
 
   // Points to the child source elements, used to iterate through the children
-  // when selecting a resource to load.
-  RefPtr<nsRange> mSourcePointer;
+  // when selecting a resource to load.  This is the index of the child element
+  // that is the current 'candidate' in:
+  // https://html.spec.whatwg.org/multipage/media.html#concept-media-load-algorithm
+  uint32_t mSourcePointer;
 
   // Points to the document whose load we're blocking. This is the document
   // we're bound to when loading starts.