Added more DCHECKs in AXNode ensuring that a tree update is not in progress

When navigating the unignored nodes in the accessibility tree and when retrieving
any node information that needs to be computed by traversing the accessibility tree,
we want to ensure that a tree update is not in progress.
This patch adds such DCHECKs in more methods in AXNode.
The only methods that are not guarded are those that get or set data members directly,
e.g. IndexInParent() and SetIndexInParent(), and those that are used to traverse the
whole tree, such as parent() and NextSibling(), as those may be called from AXTree while an update is in progress, in order to
populate the AXNode.

R=dmazzoni@chromium.org, aleventhal@chromium.org

AX-Relnotes: n/a.
Change-Id: I92c34991bf4b0583dd09bb061db9ff35c8014e9d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2623288
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842714}

ui/accessibility/ax_node.cc

@@ -89,6 +89,7 @@ AXNode* AXNode::GetLastUnignoredChild() const {
 }
 
 AXNode* AXNode::GetDeepestFirstUnignoredChild() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   if (!GetUnignoredChildCount())
     return nullptr;
 
@@ -101,6 +102,7 @@ AXNode* AXNode::GetDeepestFirstUnignoredChild() const {
 }
 
 AXNode* AXNode::GetDeepestLastUnignoredChild() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   if (!GetUnignoredChildCount())
     return nullptr;
 
@@ -287,6 +289,7 @@ AXNode* AXNode::GetPreviousUnignoredSibling() const {
 }
 
 AXNode* AXNode::GetNextUnignoredInTreeOrder() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   if (GetUnignoredChildCount())
     return GetFirstUnignoredChild();
 
@@ -303,6 +306,7 @@ AXNode* AXNode::GetNextUnignoredInTreeOrder() const {
 }
 
 AXNode* AXNode::GetPreviousUnignoredInTreeOrder() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   AXNode* sibling = GetPreviousUnignoredSibling();
   if (!sibling)
     return GetUnignoredParent();
@@ -419,6 +423,7 @@ bool AXNode::IsDescendantOf(const AXNode* ancestor) const {
 }
 
 std::vector<int> AXNode::GetOrComputeLineStartOffsets() {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   std::vector<int> line_offsets;
   if (data().GetIntListAttribute(ax::mojom::IntListAttribute::kCachedLineStarts,
                                  &line_offsets)) {
@@ -434,6 +439,7 @@ std::vector<int> AXNode::GetOrComputeLineStartOffsets() {
 
 void AXNode::ComputeLineStartOffsets(std::vector<int>* line_offsets,
                                      int* start_offset) const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   DCHECK(line_offsets);
   DCHECK(start_offset);
   for (const AXNode* child : children()) {
@@ -487,6 +493,7 @@ void AXNode::ClearLanguageInfo() {
 }
 
 std::string AXNode::GetHypertext() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   if (IsLeaf())
     return GetInnerText();
 
@@ -509,6 +516,7 @@ std::string AXNode::GetHypertext() const {
 }
 
 std::string AXNode::GetInnerText() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   // If a text field has no descendants, then we compute its inner text from its
   // value or its placeholder. Otherwise we prefer to look at its descendant
   // text nodes because Blink doesn't always add all trailing white space to the
@@ -569,6 +577,7 @@ std::string AXNode::GetInnerText() const {
 }
 
 std::string AXNode::GetLanguage() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   // Walk up tree considering both detected and author declared languages.
   for (const AXNode* cur = this; cur; cur = cur->parent()) {
     // If language detection has assigned a language then we prefer that.
@@ -588,6 +597,7 @@ std::string AXNode::GetLanguage() const {
 }
 
 std::string AXNode::GetValueForControl() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   if (data().IsTextField())
     return GetValueForTextField();
   if (data().IsRangeValueSupported())
@@ -608,6 +618,7 @@ bool AXNode::IsTable() const {
 }
 
 base::Optional<int> AXNode::GetTableColCount() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return base::nullopt;
@@ -615,6 +626,7 @@ base::Optional<int> AXNode::GetTableColCount() const {
 }
 
 base::Optional<int> AXNode::GetTableRowCount() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return base::nullopt;
@@ -622,6 +634,7 @@ base::Optional<int> AXNode::GetTableRowCount() const {
 }
 
 base::Optional<int> AXNode::GetTableAriaColCount() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return base::nullopt;
@@ -629,6 +642,7 @@ base::Optional<int> AXNode::GetTableAriaColCount() const {
 }
 
 base::Optional<int> AXNode::GetTableAriaRowCount() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return base::nullopt;
@@ -636,6 +650,7 @@ base::Optional<int> AXNode::GetTableAriaRowCount() const {
 }
 
 base::Optional<int> AXNode::GetTableCellCount() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return base::nullopt;
@@ -644,6 +659,7 @@ base::Optional<int> AXNode::GetTableCellCount() const {
 }
 
 base::Optional<bool> AXNode::GetTableHasColumnOrRowHeaderNode() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return base::nullopt;
@@ -652,6 +668,7 @@ base::Optional<bool> AXNode::GetTableHasColumnOrRowHeaderNode() const {
 }
 
 AXNode* AXNode::GetTableCellFromIndex(int index) const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return nullptr;
@@ -665,6 +682,7 @@ AXNode* AXNode::GetTableCellFromIndex(int index) const {
 }
 
 AXNode* AXNode::GetTableCaption() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return nullptr;
@@ -673,6 +691,7 @@ AXNode* AXNode::GetTableCaption() const {
 }
 
 AXNode* AXNode::GetTableCellFromCoords(int row_index, int col_index) const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return nullptr;
@@ -688,6 +707,7 @@ AXNode* AXNode::GetTableCellFromCoords(int row_index, int col_index) const {
 }
 
 std::vector<AXNode::AXID> AXNode::GetTableColHeaderNodeIds() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return std::vector<AXNode::AXID>();
@@ -705,6 +725,7 @@ std::vector<AXNode::AXID> AXNode::GetTableColHeaderNodeIds() const {
 
 std::vector<AXNode::AXID> AXNode::GetTableColHeaderNodeIds(
     int col_index) const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return std::vector<AXNode::AXID>();
@@ -717,6 +738,7 @@ std::vector<AXNode::AXID> AXNode::GetTableColHeaderNodeIds(
 
 std::vector<AXNode::AXID> AXNode::GetTableRowHeaderNodeIds(
     int row_index) const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return std::vector<AXNode::AXID>();
@@ -728,6 +750,7 @@ std::vector<AXNode::AXID> AXNode::GetTableRowHeaderNodeIds(
 }
 
 std::vector<AXNode::AXID> AXNode::GetTableUniqueCellIds() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   const AXTableInfo* table_info = GetAncestorTableInfo();
   if (!table_info)
     return std::vector<AXNode::AXID>();
@@ -736,6 +759,7 @@ std::vector<AXNode::AXID> AXNode::GetTableUniqueCellIds() const {
 }
 
 const std::vector<AXNode*>* AXNode::GetExtraMacNodes() const {
+  DCHECK(!tree_->GetTreeUpdateInProgressState());
   // Should only be available on the table node itself, not any of its children.
   const AXTableInfo* table_info = tree_->GetTableInfo(this);
   if (!table_info)