Increase heap limit for DevTools isolate.

third_party/WebKit/Source/web/WebDevToolsFrontendImpl.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 47 matching lines @@
 }
 
 WebDevToolsFrontendImpl::~WebDevToolsFrontendImpl() {
   if (m_devtoolsHost)
     m_devtoolsHost->disconnectClient();
 }
 
 void WebDevToolsFrontendImpl::didClearWindowObject(WebLocalFrameImpl* frame) {
   if (m_webFrame == frame) {
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
+    // Use higher limit for DevTools isolate so that it does not OOM when
+    // taking large heap snapshots.
+    isolate->IncreaseHeapLimitForDebugging();

[alph, 2017/01/12 17:03:22]

I wonder why it helps. Most of the heap snapshot data (nodes and edges) are
stored in external arrays. The only thing which is within the heap is strings.
However they shouldn't occupy more space than they do in the inspected heap.
Moreover, each snapshot is stored in a dedicated worker heap, so increasing main
isolate heap should have no effect.

Do you have an example page that OOMs? I'm curious to take a look.. 

     ScriptState* scriptState = ScriptState::forMainWorld(m_webFrame->frame());
     DCHECK(scriptState);
     ScriptState::Scope scope(scriptState);
 
     if (m_devtoolsHost)
       m_devtoolsHost->disconnectClient();
     m_devtoolsHost = DevToolsHost::create(this, m_webFrame->frame());
     v8::Local<v8::Object> global = scriptState->context()->Global();
     v8::Local<v8::Value> devtoolsHostObj =
         ToV8(m_devtoolsHost.get(), global, scriptState->isolate());
@@ skipping 35 matching lines @@
       ->viewImpl()
       ->showContextMenuAtPoint(x, y, menuProvider);
 }
 
 void WebDevToolsFrontendImpl::setInjectedScriptForOrigin(const String& origin,
                                                          const String& source) {
   m_injectedScriptForOrigin.set(origin, source);
 }
 
 }  // namespace blink