Bug 1753786 - Make `nsRange::ExcludeNonSelectableNodes` stop using `ErrorResult` r=mbrodesser

It never returns error since its return type is `void` and it does not take
out param whose type is `ErrorResult`.

Therefore, `ErrorResult` in it is used only for checking whether an error occurs
in the calling methods, but neither `SuppressException()` nor `StealNSResult()`
is called for avoiding assertions at destructing the instance.

For avoiding the assertion, and in this case, it should not use `ErrorResult`.
When the result is completely ignored, `IgnoreErrors()` should be used instead.
Otherwise, when it just needs to know whether an API call failed or not, it
should use `IgnoreErrors` to avoid the redundant calls of `ErrorResult` and
for the performance (`ErrorResult`'s destruction may appear in the profile if
it's used in a hot path).

Differential Revision: https://phabricator.services.mozilla.com/D138231

dom/base/nsRange.cpp

@@ -2985,7 +2985,6 @@ void nsRange::ExcludeNonSelectableNodes(nsTArray<RefPtr<nsRange>>* aOutRanges) {
     // the outer loop.
     nsIContent* firstNonSelectableContent = nullptr;
     while (true) {
-      ErrorResult err;
       nsINode* node = preOrderIter.GetCurrentNode();
       preOrderIter.Next();
       bool selectable = true;
@@ -3013,63 +3012,71 @@ void nsRange::ExcludeNonSelectableNodes(nsTArray<RefPtr<nsRange>>* aOutRanges) {
         if (!firstNonSelectableContent) {
           firstNonSelectableContent = content;
         }
-        if (preOrderIter.IsDone() && seenSelectable) {
-          // The tail end of the initial range is non-selectable - truncate the
-          // current range before the first non-selectable node.
-          range->SetEndBefore(*firstNonSelectableContent, err);
+        if (preOrderIter.IsDone()) {
+          if (seenSelectable) {
+            // The tail end of the initial range is non-selectable - truncate
+            // the current range before the first non-selectable node.
+            range->SetEndBefore(*firstNonSelectableContent, IgnoreErrors());
+          }
+          return;
         }
-      } else if (firstNonSelectableContent) {
+        continue;
+      }
+
+      if (firstNonSelectableContent) {
         if (range == this && !seenSelectable) {
           // This is the initial range and all its nodes until now are
           // non-selectable so just trim them from the start.
+          IgnoredErrorResult err;
           range->SetStartBefore(*node, err);
           if (err.Failed()) {
             return;
           }
           break;  // restart the same range with a new iterator
-        } else {
-          // Save the end point before truncating the range.
-          nsINode* endContainer = range->mEnd.Container();
-          const uint32_t endOffset =
-              *range->mEnd.Offset(RangeBoundary::OffsetFilter::kValidOffsets);
-
-          // Truncate the current range before the first non-selectable node.
-          range->SetEndBefore(*firstNonSelectableContent, err);
-
-          // Store it in the result (strong ref) - do this before creating
-          // a new range in |newRange| below so we don't drop the last ref
-          // to the range created in the previous iteration.
-          if (!added && !err.Failed()) {
-            aOutRanges->AppendElement(range);
-          }
-
-          // Create a new range for the remainder.
-          nsINode* startContainer = node;
-          Maybe<uint32_t> startOffset = Some(0);
-          // Don't start *inside* a node with independent selection though
-          // (e.g. <input>).
-          if (content && content->HasIndependentSelection()) {
-            nsINode* parent = startContainer->GetParent();
-            if (parent) {
-              startOffset = parent->ComputeIndexOf(startContainer);
-              startContainer = parent;
-            }
-          }
-          newRange =
-              nsRange::Create(startContainer, startOffset.valueOr(UINT32_MAX),
-                              endContainer, endOffset, IgnoreErrors());
-          if (!newRange || newRange->Collapsed()) {
-            newRange = nullptr;
-          }
-          range = newRange;
-          break;  // create a new iterator for the new range, if any
         }
-      } else {
-        seenSelectable = true;
-        if (!added) {
-          added = true;
+
+        // Save the end point before truncating the range.
+        nsINode* endContainer = range->mEnd.Container();
+        const uint32_t endOffset =
+            *range->mEnd.Offset(RangeBoundary::OffsetFilter::kValidOffsets);
+
+        // Truncate the current range before the first non-selectable node.
+        IgnoredErrorResult err;
+        range->SetEndBefore(*firstNonSelectableContent, err);
+
+        // Store it in the result (strong ref) - do this before creating
+        // a new range in |newRange| below so we don't drop the last ref
+        // to the range created in the previous iteration.
+        if (!added && !err.Failed()) {
           aOutRanges->AppendElement(range);
         }
+
+        // Create a new range for the remainder.
+        nsINode* startContainer = node;
+        Maybe<uint32_t> startOffset = Some(0);
+        // Don't start *inside* a node with independent selection though
+        // (e.g. <input>).
+        if (content && content->HasIndependentSelection()) {
+          nsINode* parent = startContainer->GetParent();
+          if (parent) {
+            startOffset = parent->ComputeIndexOf(startContainer);
+            startContainer = parent;
+          }
+        }
+        newRange =
+            nsRange::Create(startContainer, startOffset.valueOr(UINT32_MAX),
+                            endContainer, endOffset, IgnoreErrors());
+        if (!newRange || newRange->Collapsed()) {
+          newRange = nullptr;
+        }
+        range = newRange;
+        break;  // create a new iterator for the new range, if any
+      }
+
+      seenSelectable = true;
+      if (!added) {
+        added = true;
+        aOutRanges->AppendElement(range);
       }
       if (preOrderIter.IsDone()) {
         return;

testing/web-platform/tests/editing/crashtests/selectall-selection-modify-move-forward-lineboundary-selectall-around-editable-canvas.html

@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<script>
+onload = () => {
+  document.querySelector("canvas[contenteditable]").blur();
+  document.execCommand("selectAll", false);
+  getSelection().modify("move", "forward", "lineboundary");
+  document.execCommand("selectAll", false);
+};
+</script>
+<canvas contenteditable="true">
+<audio controls>