Add RELEASE_ASSERT to InlineTextBox::constructTextRun

third_party/WebKit/Source/core/layout/line/InlineTextBox.cpp

Index: third_party/WebKit/Source/core/layout/line/InlineTextBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/line/InlineTextBox.cpp b/third_party/WebKit/Source/core/layout/line/InlineTextBox.cpp
index 0dbf55c9d824a9a274c7926f7e30170c133a3824..6d01393db84bc2aaec7e7c0963a411d8d7199a74 100644
--- a/third_party/WebKit/Source/core/layout/line/InlineTextBox.cpp
+++ b/third_party/WebKit/Source/core/layout/line/InlineTextBox.cpp
@@ -616,6 +616,10 @@ TextRun InlineTextBox::constructTextRun(
   String string = getLineLayoutItem().text();
   unsigned startPos = start();
   unsigned length = len();
+  // Ensure |this| is in sync with the corresponding LayoutText. Checking here
+  // has less binary size/perf impact than in StringView().
+  RELEASE_ASSERT(startPos <= string.length() &&
+                 length <= string.length() - startPos);
   return constructTextRun(style, StringView(string, startPos, length),
                           getLineLayoutItem().textLength() - startPos,
                           charactersWithHyphen);