BackgroundHTMLParser: Make token limits unconfigurable

I couldn't find any occurrence in tests that attempt to dynamically reconfigure this.
This CL just makes them use constants to reduce complexity.

Bug: 689702
Change-Id: I431aaec674a439d82499a1b4099d4de64e75f5c1
Reviewed-on: https://chromium-review.googlesource.com/1032313
Commit-Queue: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554343}

third_party/blink/renderer/core/frame/settings.json5

@@ -530,19 +530,6 @@
       type: "ImageAnimationPolicy",
     },
 
-    // Number of outstanding and pending tokens allowed in the background HTML
-    // parser. A value of 0 indicates the parser should use its default value.
-    {
-      name: "backgroundHtmlParserOutstandingTokenLimit",
-      initial: 0,
-      type: "unsigned",
-    },
-    {
-      name: "backgroundHtmlParserPendingTokenLimit",
-      initial: 0,
-      type: "unsigned",
-    },
-
     // Html preload scanning is a fast, early scan of HTML documents to find loadable
     // resources before the parser advances to them. If it is disabled, resources will
     // be loaded later.

third_party/blink/renderer/core/html/parser/background_html_parser.cc

@@ -50,19 +50,21 @@ namespace blink {
 // potentially time if the speculation fails). So we limit our outstanding
 // tokens arbitrarily to 10,000. Our maximal memory spent speculating will be
 // approximately:
-// (defaultOutstandingTokenLimit + defaultPendingTokenLimit) *
-// sizeof(CompactToken)
+// (kOutstandingTokenLimit + kPendingTokenLimit) * sizeof(CompactToken)
 //
 // We use a separate low and high water mark to avoid
 // constantly topping off the main thread's token buffer. At time of writing,
 // this is (10000 + 1000) * 28 bytes = ~308kb of memory. These numbers have not
 // been tuned.
-static const size_t kDefaultOutstandingTokenLimit = 10000;
+static const size_t kOutstandingTokenLimit = 10000;
 
 // We limit our chucks to 1000 tokens, to make sure the main thread is never
 // waiting on the parser thread for tokens. This was tuned in
 // https://bugs.webkit.org/show_bug.cgi?id=110408.
-static const size_t kDefaultPendingTokenLimit = 1000;
+static const size_t kPendingTokenLimit = 1000;
+
+static_assert(kOutstandingTokenLimit > kPendingTokenLimit,
+              "Outstanding token limit is applied after pending token limit.");
 
 using namespace HTMLNames;
 
@@ -106,9 +108,7 @@ void BackgroundHTMLParser::Init(
       TokenPreloadScanner::ScannerType::kMainDocument));
 }
 
-BackgroundHTMLParser::Configuration::Configuration()
-    : outstanding_token_limit(kDefaultOutstandingTokenLimit),
-      pending_token_limit(kDefaultPendingTokenLimit) {}
+BackgroundHTMLParser::Configuration::Configuration() {}
 
 BackgroundHTMLParser::BackgroundHTMLParser(
     std::unique_ptr<Configuration> config,
@@ -117,9 +117,7 @@ BackgroundHTMLParser::BackgroundHTMLParser(
       tokenizer_(HTMLTokenizer::Create(config->options)),
       tree_builder_simulator_(config->options),
       options_(config->options),
-      outstanding_token_limit_(config->outstanding_token_limit),
       parser_(config->parser),
-      pending_token_limit_(config->pending_token_limit),
       xss_auditor_(std::move(config->xss_auditor)),
       decoder_(std::move(config->decoder)),
       loading_task_runner_(std::move(loading_task_runner)),
@@ -127,9 +125,6 @@ BackgroundHTMLParser::BackgroundHTMLParser(
           HTMLDocumentParser::TokenizedChunk::kNoPendingToken),
       starting_script_(false),
       weak_factory_(this) {
-  DCHECK_GT(outstanding_token_limit_, 0u);
-  DCHECK_GT(pending_token_limit_, 0u);
-  DCHECK_GE(outstanding_token_limit_, pending_token_limit_);
 }
 
 BackgroundHTMLParser::~BackgroundHTMLParser() = default;
@@ -223,7 +218,7 @@ void BackgroundHTMLParser::PumpTokenizer() {
       HTMLTreeBuilderSimulator::kOtherToken;
 
   // No need to start speculating until the main thread has almost caught up.
-  if (input_.TotalCheckpointTokenCount() > outstanding_token_limit_)
+  if (input_.TotalCheckpointTokenCount() > kOutstandingTokenLimit)
     return;
 
   while (true) {
@@ -277,12 +272,12 @@ void BackgroundHTMLParser::PumpTokenizer() {
     if (simulated_token == HTMLTreeBuilderSimulator::kScriptEnd ||
         simulated_token == HTMLTreeBuilderSimulator::kStyleEnd ||
         simulated_token == HTMLTreeBuilderSimulator::kLink ||
-        pending_tokens_.size() >= pending_token_limit_) {
+        pending_tokens_.size() >= kPendingTokenLimit) {
       EnqueueTokenizedChunk();
 
       // If we're far ahead of the main thread, yield for a bit to avoid
       // consuming too much memory.
-      if (input_.TotalCheckpointTokenCount() > outstanding_token_limit_)
+      if (input_.TotalCheckpointTokenCount() > kOutstandingTokenLimit)
         break;
     }
   }

third_party/blink/renderer/core/html/parser/background_html_parser.h

@@ -59,10 +59,6 @@ class BackgroundHTMLParser {
     base::WeakPtr<HTMLDocumentParser> parser;
     std::unique_ptr<XSSAuditor> xss_auditor;
     std::unique_ptr<TextResourceDecoder> decoder;
-    // outstandingTokenLimit must be greater than or equal to
-    // pendingTokenLimit
-    size_t outstanding_token_limit;
-    size_t pending_token_limit;
   };
 
   // The returned BackgroundHTMLParser should only be used on the parser
@@ -119,11 +115,9 @@ class BackgroundHTMLParser {
   std::unique_ptr<HTMLTokenizer> tokenizer_;
   HTMLTreeBuilderSimulator tree_builder_simulator_;
   HTMLParserOptions options_;
-  const size_t outstanding_token_limit_;
   base::WeakPtr<HTMLDocumentParser> parser_;
 
   CompactHTMLTokenStream pending_tokens_;
-  const size_t pending_token_limit_;
   PreloadRequestStream pending_preloads_;
   ViewportDescriptionWrapper viewport_description_;
   XSSInfoStream pending_xss_infos_;

third_party/blink/renderer/core/html/parser/html_document_parser.cc

@@ -37,7 +37,6 @@
 #include "third_party/blink/renderer/core/dom/document_fragment.h"
 #include "third_party/blink/renderer/core/dom/element.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
-#include "third_party/blink/renderer/core/frame/settings.h"
 #include "third_party/blink/renderer/core/html/html_document.h"
 #include "third_party/blink/renderer/core/html/parser/atomic_html_token.h"
 #include "third_party/blink/renderer/core/html/parser/background_html_parser.h"
@@ -803,24 +802,6 @@ void HTMLDocumentParser::StartBackgroundParser() {
   config->xss_auditor->Init(GetDocument(), &xss_auditor_delegate_);
 
   config->decoder = TakeDecoder();
-  if (GetDocument()->GetSettings()) {
-    if (GetDocument()
-            ->GetSettings()
-            ->GetBackgroundHtmlParserOutstandingTokenLimit()) {
-      config->outstanding_token_limit =
-          GetDocument()
-              ->GetSettings()
-              ->GetBackgroundHtmlParserOutstandingTokenLimit();
-    }
-    if (GetDocument()
-            ->GetSettings()
-            ->GetBackgroundHtmlParserPendingTokenLimit()) {
-      config->pending_token_limit =
-          GetDocument()
-              ->GetSettings()
-              ->GetBackgroundHtmlParserPendingTokenLimit();
-    }
-  }
 
   DCHECK(config->xss_auditor->IsSafeToSendToAnotherThread());