Fix null deref inside DCHECK

TBR=nektar@chromium.org

Bug: None
Change-Id: If65d7e630b152a48759be2016928895a06094b89
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2530209Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825982}

content/browser/accessibility/browser_accessibility.cc

@@ -70,8 +70,11 @@ const BrowserAccessibility* GetTextContainerForPlainTextField(
   if (child->InternalChildCount() == 1) {
     const BrowserAccessibility* grand_child = child->InternalGetFirstChild();
     if (grand_child->GetRole() == ax::mojom::Role::kGenericContainer) {
-      DCHECK_EQ(grand_child->InternalGetFirstChild()->GetRole(),
-                ax::mojom::Role::kStaticText);
+      // There is not always a static text child of the grandchild, but if there
+      // is, it must be static text.
+      DCHECK(!grand_child->InternalGetFirstChild() ||
+             grand_child->InternalGetFirstChild()->GetRole() ==
+                 ax::mojom::Role::kStaticText);
       return grand_child;
     }
     DCHECK_EQ(child->InternalGetFirstChild()->GetRole(),