【v8阅读_1】

1. third_party/blink/renderer/core/execution_context/execution_context.h — ExecutionContext

网络上有个误区，其实我们以前理解的所谓的 “执行上下文” 不是 chromium 里的 ExecutionContext
而是 v8::Context 及其相关内容！！很容易想到啊，js是由v8控制解释的，肯定v8说的算啊
这个文件下那大段注释英文也说了，这俩不是同一个东西

// An environment in which script can execute. This class exposes the common
// properties of script execution environments on the web (i.e, common between
// script executing in a window and script executing in a worker), such as:
//
// - a base URL for the resolution of relative URLs
// - a security context that defines the privileges associated with the
//   environment (note, however, that specific isolated script contexts may
//   still enjoy elevated privileges)
// - affordances for the activity (including script and active DOM objects) to
//   be paused or terminated, e.g. because a frame has entered the background or
//   been closed permanently
// - a console logging facility for debugging
//
// Typically, the ExecutionContext is an instance of LocalDOMWindow or of
// WorkerOrWorkletGlobalScope.
//
// Note that this is distinct from the notion of a ScriptState or v8::Context,
// which are associated with a single script context (with a single global
// object). For example, there are separate JavaScript globals for "main world"
// script written by a web author and an "isolated world" content script written
// by an extension developer, but these share an ExecutionContext (the window)
// in common.
可以执行脚本的环境。该类公开了网络上脚本执行环境的公共属性
（即在窗口中执行的脚本和在工作器中执行的脚本之间的公共属性），例如：
- 用于解析相对 URL 的基本 URL
- 一个安全上下文，它定义了与这个环境关联的权限
 （但是请注意，特定的隔离脚本上下文可能仍然享有更高的权限）
- 要暂停或终止的活动（包括脚本和活动 DOM 对象）的可供性，例如因为框架已进入背景或永久关闭
- 用于调试的控制台日志记录工具
通常， ExecutionContext 是 LocalDOMWindow 或
WorkerOrWorkletGlobalScope。
请注意，这与 ScriptState 或 v8::Context 的概念不同，后者与单个脚本上下文（具有单个全局对象）
相关联。例如，对于由网络作者编写的“主世界”脚本和由扩展开发人员编写的“孤立世界”内容脚本，
有单独的 JavaScript 全局变量，但它们共享一个共同的 ExecutionContext（窗口）。

1. v8/include/v8-local-handle.h ```cpp /**
   • An object reference managed by the v8 garbage collector. *
   • All objects returned from v8 have to be tracked by the garbage collector so
   • that it knows that the objects are still alive. Also, because the garbage
   • collector may move objects, it is unsafe to point directly to an object.
   • Instead, all objects are stored in handles which are known by the garbage
   • collector and updated whenever an object moves. Handles should always be
   • passed by value (except in cases like out-parameters) and they should never
   • be allocated on the heap. *
   • There are two types of handles: local and persistent handles. *
   • Local handles are light-weight and transient and typically used in local
   • operations. They are managed by HandleScopes. That means that a HandleScope
   • must exist on the stack when they are created and that they are only valid
   • inside of the HandleScope active during their creation. For passing a local
   • handle to an outer HandleScope, an EscapableHandleScope and its Escape()
   • method must be used. *
   • Persistent handles can be used when storing objects across several
   • independent operations and have to be explicitly deallocated when they’re no
   • longer used. *
   • It is safe to extract the object stored in the handle by dereferencing the
   • handle (for instance, to extract the Object* from a Local