Experimental scanner: fix two-byte handling in lexer-shell.

src/lexer/lexer-shell.cc

Index: src/lexer/lexer-shell.cc
diff --git a/src/lexer/lexer-shell.cc b/src/lexer/lexer-shell.cc
index 266727ff3ffaa9bec51d889c907e15d0e38b92b6..28722f5c8bc093d493ece96482e2e9c81715bb34 100644
--- a/src/lexer/lexer-shell.cc
+++ b/src/lexer/lexer-shell.cc
@@ -295,10 +295,15 @@ std::pair<TimeDelta, TimeDelta> ProcessFile(
             Vector<const uc16>(buffer_16, buffer_end_16 - buffer_16));
         // If the string was just an expaneded one byte string, V8 detects it
         // and doesn't store it as two byte.
-        CHECK(source->IsTwoByteRepresentation());
-        experimental_time = RunExperimentalScanner<uint16_t>(
-            source, isolate, encoding, print_tokens || check_tokens,
-            &experimental_tokens, repeat, harmony_settings);
+        if (!source->IsTwoByteRepresentation()) {
+          experimental_time = RunExperimentalScanner<uint8_t>(
+              source, isolate, encoding, print_tokens || check_tokens,
+              &experimental_tokens, repeat, harmony_settings);
+        } else {
+          experimental_time = RunExperimentalScanner<uint16_t>(
+              source, isolate, encoding, print_tokens || check_tokens,
+              &experimental_tokens, repeat, harmony_settings);
+        }
         break;
       }
       default: