Revert "[scanner] Add Skip to be used after successful Peek"

This reverts commit 7fb6109b.

Reason for revert: Speculatively reverting because of https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8-Blink%20Linux%2064%20(dbg)/13264

Original change's description:
> [scanner] Add Skip to be used after successful Peek
> 
> Change-Id: Ic3df370e2859bf77572b34a314ad8ed17b75b942
> Reviewed-on: https://chromium-review.googlesource.com/1183485
> Commit-Queue: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55279}

TBR=leszeks@chromium.org,verwaest@chromium.org

Change-Id: Ie1825cb4c971d2ec6a00b7ce3384c97ebbf885ce
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1184922Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55301}

src/parsing/scanner.cc

@@ -529,8 +529,7 @@ Token::Value Scanner::ScanHtmlComment() {
     PushBack('!');  // undo Advance()
     return Token::LT;
   }
-  source_->Skip('-');
-  DCHECK_EQ('-', c0_);
+  Advance();
 
   found_html_comment_ = true;
   return SkipSingleHTMLComment();
@@ -675,7 +674,7 @@ void Scanner::Scan() {
         if (c0_ == '/') {
           uc32 c = Peek();
           if (c == '#' || c == '@') {
-            source_->Skip(c);
+            Advance();
             Advance();
             token = SkipSourceURLComment();
           } else {
@@ -728,7 +727,7 @@ void Scanner::Scan() {
           token = Token::PERIOD;
           if (c0_ == '.') {
             if (Peek() == '.') {
-              source_->Skip('.');
+              Advance();
               Advance();
               token = Token::ELLIPSIS;
             }
@@ -1005,8 +1004,8 @@ Token::Value Scanner::ScanTemplateSpan() {
       result = Token::TEMPLATE_TAIL;
       break;
     } else if (c == '$' && Peek() == '{') {
-      source_->Skip('{');
-      Advance();
+      Advance();  // Consume '$'
+      Advance();  // Consume '{'
       break;
     } else if (c == '\\') {
       Advance();  // Consume '\\'

src/parsing/scanner.h

@@ -50,12 +50,6 @@ class Utf16CharacterStream {
     }
   }
 
-  inline void Skip(uc32 c) {
-    DCHECK_LT(buffer_cursor_, buffer_end_);
-    DCHECK_EQ(c, static_cast<uc32>(*buffer_cursor_));
-    buffer_cursor_++;
-  }
-
   // Returns and advances past the next UTF-16 code unit in the input
   // stream. If there are no more code units it returns kEndOfInput.
   inline uc32 Advance() {
@@ -640,13 +634,13 @@ class Scanner {
   bool CombineSurrogatePair() {
     DCHECK(!unibrow::Utf16::IsLeadSurrogate(kEndOfInput));
     if (unibrow::Utf16::IsLeadSurrogate(c0_)) {
-      uc32 c1 = source_->Peek();
+      uc32 c1 = source_->Advance();
       DCHECK(!unibrow::Utf16::IsTrailSurrogate(kEndOfInput));
       if (unibrow::Utf16::IsTrailSurrogate(c1)) {
         c0_ = unibrow::Utf16::CombineSurrogatePair(c0_, c1);
-        source_->Skip(c1);
         return true;
       }
+      source_->Back();
     }
     return false;
   }