--- a/accessible/ipc/ProxyAccessible.cpp
+++ b/accessible/ipc/ProxyAccessible.cpp
@@ -515,25 +515,37 @@ uint32_t
 ProxyAccessible::RowExtent()
 {
   uint32_t extent = 0;
   unused << mDoc->SendRowExtent(mID, &extent);
   return extent;
 }
 
 void
-ProxyAccessible::ColHeaderCells(nsTArray<uint64_t>* aCells)
+ProxyAccessible::ColHeaderCells(nsTArray<ProxyAccessible*>* aCells)
 {
-  unused << mDoc->SendColHeaderCells(mID, aCells);
+  nsTArray<uint64_t> targetIDs;
+  unused << mDoc->SendColHeaderCells(mID, &targetIDs);
+
+  size_t targetCount = targetIDs.Length();
+  for (size_t i = 0; i < targetCount; i++) {
+    aCells->AppendElement(mDoc->GetAccessible(targetIDs[i]));
+  }
 }
 
 void
-ProxyAccessible::RowHeaderCells(nsTArray<uint64_t>* aCells)
+ProxyAccessible::RowHeaderCells(nsTArray<ProxyAccessible*>* aCells)
 {
-  unused << mDoc->SendRowHeaderCells(mID, aCells);
+  nsTArray<uint64_t> targetIDs;
+  unused << mDoc->SendRowHeaderCells(mID, &targetIDs);
+
+  size_t targetCount = targetIDs.Length();
+  for (size_t i = 0; i < targetCount; i++) {
+    aCells->AppendElement(mDoc->GetAccessible(targetIDs[i]));
+  }
 }
 
 bool
 ProxyAccessible::IsCellSelected()
 {
   bool selected = false;
   unused << mDoc->SendIsCellSelected(mID, &selected);
   return selected;

--- a/accessible/ipc/ProxyAccessible.h
+++ b/accessible/ipc/ProxyAccessible.h
@@ -219,19 +219,19 @@ public:
   uint32_t ColIdx();
 
   uint32_t RowIdx();
 
   uint32_t ColExtent();
 
   uint32_t RowExtent();
 
-  void ColHeaderCells(nsTArray<uint64_t>* aCells);
+  void ColHeaderCells(nsTArray<ProxyAccessible*>* aCells);
 
-  void RowHeaderCells(nsTArray<uint64_t>* aCells);
+  void RowHeaderCells(nsTArray<ProxyAccessible*>* aCells);
 
   bool IsCellSelected();
 
   ProxyAccessible* TableCaption();
   void TableSummary(nsString& aSummary);
   uint32_t TableColumnCount();
   uint32_t TableRowCount();
   ProxyAccessible* TableCellAt(uint32_t aRow, uint32_t aCol);

--- a/accessible/mac/moz.build
+++ b/accessible/mac/moz.build
@@ -35,9 +35,11 @@ LOCAL_INCLUDES += [
     '/layout/generic',
     '/layout/xul',
     '/widget',
     '/widget/cocoa',
 ]
 
 FINAL_LIBRARY = 'xul'
 
+include('/ipc/chromium/chromium-config.mozbuild')
+
 FAIL_ON_WARNINGS = True

--- a/accessible/mac/mozAccessible.mm
+++ b/accessible/mac/mozAccessible.mm
@@ -13,16 +13,17 @@
 #include "nsIAccessibleRelation.h"
 #include "nsIAccessibleEditableText.h"
 #include "nsIPersistentProperties2.h"
 #include "Relation.h"
 #include "Role.h"
 #include "RootAccessible.h"
 #include "TableAccessible.h"
 #include "TableCellAccessible.h"
+#include "mozilla/a11y/PDocAccessible.h"
 
 #include "mozilla/Services.h"
 #include "nsRect.h"
 #include "nsCocoaUtils.h"
 #include "nsCoord.h"
 #include "nsObjCExceptions.h"
 #include "nsWhitespaceTokenizer.h"
 #include <prdtoa.h>
@@ -365,17 +366,18 @@ ConvertToNSArray(nsTArray<ProxyAccessibl
   NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
 }
 
 - (id)accessibilityAttributeValue:(NSString*)attribute
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;
 
   AccessibleWrap* accWrap = [self getGeckoAccessible];
-  if (!accWrap)
+  ProxyAccessible* proxy = [self getProxyAccessible];
+  if (!accWrap && !proxy)
     return nil;
 
 #if DEBUG
   if ([attribute isEqualToString:@"AXMozDescription"])
     return [NSString stringWithFormat:@"role = %u native = %@", mRole, [self class]];
 #endif
 
   if ([attribute isEqualToString:NSAccessibilityChildrenAttribute])
@@ -407,72 +409,127 @@ ConvertToNSArray(nsTArray<ProxyAccessibl
     return [self size];
   if ([attribute isEqualToString:NSAccessibilityWindowAttribute])
     return [self window];
   if ([attribute isEqualToString:NSAccessibilityTopLevelUIElementAttribute])
     return [self window];
   if ([attribute isEqualToString:NSAccessibilityTitleAttribute])
     return [self title];
   if ([attribute isEqualToString:NSAccessibilityTitleUIElementAttribute]) {
-    Relation rel =
-      accWrap->RelationByType(RelationType::LABELLED_BY);
-    Accessible* tempAcc = rel.Next();
-    return tempAcc ? GetNativeFromGeckoAccessible(tempAcc) : nil;
+    if (accWrap) {
+      Relation rel = accWrap->RelationByType(RelationType::LABELLED_BY);
+      Accessible* tempAcc = rel.Next();
+      return tempAcc ? GetNativeFromGeckoAccessible(tempAcc) : nil;
+    }
+    nsTArray<ProxyAccessible*> rel = proxy->RelationByType(RelationType::LABELLED_BY);
+    ProxyAccessible* tempProxy = rel.SafeElementAt(0);
+    return tempProxy ? GetNativeFromProxy(tempProxy) : nil;
   }
   if ([attribute isEqualToString:NSAccessibilityHelpAttribute])
     return [self help];
 
-  if (accWrap->IsTable()) {
-    TableAccessible* table = accWrap->AsTable();
-    if ([attribute isEqualToString:NSAccessibilityRowCountAttribute])
-      return @(table->RowCount());
-    if ([attribute isEqualToString:NSAccessibilityColumnCountAttribute])
-      return @(table->ColCount());
-    if ([attribute isEqualToString:NSAccessibilityRowsAttribute]) {
-      // Create a new array with the list of table rows.
-      NSMutableArray* nativeArray = [[NSMutableArray alloc] init];
-      uint32_t totalCount = accWrap->ChildCount();
-      for (uint32_t i = 0; i < totalCount; i++) {
-        if (accWrap->GetChildAt(i)->IsTableRow()) {
-          mozAccessible* curNative =
-            GetNativeFromGeckoAccessible(accWrap->GetChildAt(i));
-          if (curNative)
-            [nativeArray addObject:GetObjectOrRepresentedView(curNative)];
+  if (accWrap) {
+    if (accWrap->IsTable()) {
+      TableAccessible* table = accWrap->AsTable();
+      if ([attribute isEqualToString:NSAccessibilityRowCountAttribute])
+        return @(table->RowCount());
+      if ([attribute isEqualToString:NSAccessibilityColumnCountAttribute])
+        return @(table->ColCount());
+      if ([attribute isEqualToString:NSAccessibilityRowsAttribute]) {
+        // Create a new array with the list of table rows.
+        NSMutableArray* nativeArray = [[NSMutableArray alloc] init];
+        uint32_t totalCount = accWrap->ChildCount();
+        for (uint32_t i = 0; i < totalCount; i++) {
+          if (accWrap->GetChildAt(i)->IsTableRow()) {
+            mozAccessible* curNative =
+              GetNativeFromGeckoAccessible(accWrap->GetChildAt(i));
+            if (curNative)
+              [nativeArray addObject:GetObjectOrRepresentedView(curNative)];
+          }
         }
+        return nativeArray;
       }
-      return nativeArray;
+    } else if (accWrap->IsTableRow()) {
+      if ([attribute isEqualToString:NSAccessibilityIndexAttribute]) {
+        // Count the number of rows before that one to obtain the row index.
+        uint32_t index = 0;
+        for (int32_t i = accWrap->IndexInParent() - 1; i >= 0; i--) {
+          if (accWrap->GetChildAt(i)->IsTableRow()) {
+            index++;
+          }
+        }
+        return [NSNumber numberWithUnsignedInteger:index];
+      }
+    } else if (accWrap->IsTableCell()) {
+      TableCellAccessible* cell = accWrap->AsTableCell();
+      if ([attribute isEqualToString:NSAccessibilityRowIndexRangeAttribute])
+        return [NSValue valueWithRange:NSMakeRange(cell->RowIdx(),
+                                                   cell->RowExtent())];
+      if ([attribute isEqualToString:NSAccessibilityColumnIndexRangeAttribute])
+        return [NSValue valueWithRange:NSMakeRange(cell->ColIdx(),
+                                                   cell->ColExtent())];
+      if ([attribute isEqualToString:NSAccessibilityRowHeaderUIElementsAttribute]) {
+        nsAutoTArray<Accessible*, 10> headerCells;
+        cell->RowHeaderCells(&headerCells);
+        return ConvertToNSArray(headerCells);
+      }
+      if ([attribute isEqualToString:NSAccessibilityColumnHeaderUIElementsAttribute]) {
+        nsAutoTArray<Accessible*, 10> headerCells;
+        cell->ColHeaderCells(&headerCells);
+        return ConvertToNSArray(headerCells);
+      }
     }
-  } else if (accWrap->IsTableRow()) {
-    if ([attribute isEqualToString:NSAccessibilityIndexAttribute]) {
-      // Count the number of rows before that one to obtain the row index.
-      uint32_t index = 0;
-      for (int32_t i = accWrap->IndexInParent() - 1; i >= 0; i--) {
-        if (accWrap->GetChildAt(i)->IsTableRow()) {
-          index++;
+  } else if (proxy) {
+    if (proxy->IsTable()) {
+      if ([attribute isEqualToString:NSAccessibilityRowCountAttribute])
+        return @(proxy->TableRowCount());
+      if ([attribute isEqualToString:NSAccessibilityColumnCountAttribute])
+        return @(proxy->TableColumnCount());
+      if ([attribute isEqualToString:NSAccessibilityRowsAttribute]) {
+        // Create a new array with the list of table rows.
+        NSMutableArray* nativeArray = [[NSMutableArray alloc] init];
+        uint32_t totalCount = proxy->ChildrenCount();
+        for (uint32_t i = 0; i < totalCount; i++) {
+          if (proxy->ChildAt(i)->IsTableRow()) {
+            mozAccessible* curNative =
+              GetNativeFromProxy(proxy->ChildAt(i));
+            if (curNative)
+              [nativeArray addObject:GetObjectOrRepresentedView(curNative)];
+          }
         }
+        return nativeArray;
       }
-      return [NSNumber numberWithUnsignedInteger:index];
-    }
-  } else if (accWrap->IsTableCell()) {
-    TableCellAccessible* cell = accWrap->AsTableCell();
-    if ([attribute isEqualToString:NSAccessibilityRowIndexRangeAttribute])
-      return [NSValue valueWithRange:NSMakeRange(cell->RowIdx(),
-                                                 cell->RowExtent())];
-    if ([attribute isEqualToString:NSAccessibilityColumnIndexRangeAttribute])
-      return [NSValue valueWithRange:NSMakeRange(cell->ColIdx(),
-                                                 cell->ColExtent())];
-    if ([attribute isEqualToString:NSAccessibilityRowHeaderUIElementsAttribute]) {
-      nsAutoTArray<Accessible*, 10> headerCells;
-      cell->RowHeaderCells(&headerCells);
-      return ConvertToNSArray(headerCells);
-    }
-    if ([attribute isEqualToString:NSAccessibilityColumnHeaderUIElementsAttribute]) {
-      nsAutoTArray<Accessible*, 10> headerCells;
-      cell->ColHeaderCells(&headerCells);
-      return ConvertToNSArray(headerCells);
+    } else if (proxy->IsTableRow()) {
+      if ([attribute isEqualToString:NSAccessibilityIndexAttribute]) {
+        // Count the number of rows before that one to obtain the row index.
+        uint32_t index = 0;
+        for (int32_t i = proxy->IndexInParent() - 1; i >= 0; i--) {
+          if (proxy->ChildAt(i)->IsTableRow()) {
+            index++;
+          }
+        }
+        return [NSNumber numberWithUnsignedInteger:index];
+      }
+    } else if (proxy->IsTableCell()) {
+      if ([attribute isEqualToString:NSAccessibilityRowIndexRangeAttribute])
+        return [NSValue valueWithRange:NSMakeRange(proxy->RowIdx(),
+                                                   proxy->RowExtent())];
+      if ([attribute isEqualToString:NSAccessibilityColumnIndexRangeAttribute])
+        return [NSValue valueWithRange:NSMakeRange(proxy->ColIdx(),
+                                                   proxy->ColExtent())];
+      if ([attribute isEqualToString:NSAccessibilityRowHeaderUIElementsAttribute]) {
+        nsTArray<ProxyAccessible*> headerCells;
+        proxy->RowHeaderCells(&headerCells);
+        return ConvertToNSArray(headerCells);
+      }
+      if ([attribute isEqualToString:NSAccessibilityColumnHeaderUIElementsAttribute]) {
+        nsTArray<ProxyAccessible*> headerCells;
+        proxy->ColHeaderCells(&headerCells);
+        return ConvertToNSArray(headerCells);
+      }
     }
   }
 
   switch (mRole) {
   case roles::MATHML_ROOT:
     if ([attribute isEqualToString:NSAccessibilityMathRootRadicandAttribute])
       return [self childAt:0];
     if ([attribute isEqualToString:NSAccessibilityMathRootIndexAttribute])
@@ -491,19 +548,30 @@ ConvertToNSArray(nsTArray<ProxyAccessibl
       // WebKit sets line thickness to some logical value parsed in the
       // renderer object of the <mfrac> element. It's not clear whether the
       // exact value is relevant to assistive technologies. From a semantic
       // point of view, the only important point is to distinguish between
       // <mfrac> elements that have a fraction bar and those that do not.
       // Per the MathML 3 spec, the latter happens iff the linethickness
       // attribute is of the form [zero-float][optional-unit]. In that case we
       // set line thickness to zero and in the other cases we set it to one.
-      nsCOMPtr<nsIPersistentProperties> attributes = accWrap->Attributes();
       nsAutoString thickness;
-      nsAccUtils::GetAccAttr(attributes, nsGkAtoms::linethickness_, thickness);
+      if (accWrap) {
+        nsCOMPtr<nsIPersistentProperties> attributes = accWrap->Attributes();
+        nsAccUtils::GetAccAttr(attributes, nsGkAtoms::linethickness_, thickness);
+      } else {
+        nsAutoTArray<Attribute, 10> attrs;
+        proxy->Attributes(&attrs);
+        for (size_t i = 0 ; i < attrs.Length() ; i++) {
+          if (attrs.ElementAt(i).Name() == "thickness") {
+            thickness = attrs.ElementAt(i).Value();
+            break;
+          }
+        }
+      }
       double value = 1.0;
       if (!thickness.IsEmpty())
         value = PR_strtod(NS_LossyConvertUTF16toASCII(thickness).get(),
                           nullptr);
       return [NSNumber numberWithInteger:(value ? 1 : 0)];
     }
     break;
   case roles::MATHML_SUB: