Add support for direct communication over the DevTools protocol

[magreenblatt]

Original report by me.

---

The DevTools protocol can be used to automate behaviors in the browser. For example, projects like ChromeDriver use the DevTools protocol over a remote connection for automated testing. Access to DevTools protocol communication (methods and events) can also be exposed directly via CefBrowserHost methods for controlling behaviors such as offline mode (see issue #245). Some DevTools state is cleared on main frame (or cross-renderer) navigation so it will be necessary to additionally expose some document-related callbacks (see issue #1454).

[magreenblatt]

Add support for direct DevTools protocol messaging (fixes issue #2961).

This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.

This change includes additional supporting changes:

• Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
  callback (see issue Add callback for document element creation #1454).
• Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
• Add a --devtools-protocol-log-file=<path> command-line flag for
  logging protocol messages sent to/from the DevTools front-end
  while it is displayed. This is useful for understanding existing
  DevTools protocol usage.
• Add a new "libcef_static_unittests" executable target to support
  light-weight unit tests of libcef_static internals (e.g. without
  requiring exposure via the CEF API). Files to be unittested are
  placed in the new "libcef_static_unittested" source_set which is
  then included by both the existing libcef_static library and the
  new unittests executable target.
• Linux: Remove use_bundled_fontconfig=false, which is no longer
  required and causes unittest build errors (see issue Linux Ubuntu 16.04: Hang during startup in FT_Load_Glyph #2424).

This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the --offline
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.

→ <<cset 39aed35644dc (bb)>>

[magreenblatt]

• changed state from "new" to "resolved"

[magreenblatt]

Add support for direct DevTools protocol messaging (fixes issue #2961).

This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.

This change includes additional supporting changes:

• Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
  callback (see issue Add callback for document element creation #1454).
• Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
• Add a --devtools-protocol-log-file=<path> command-line flag for
  logging protocol messages sent to/from the DevTools front-end
  while it is displayed. This is useful for understanding existing
  DevTools protocol usage.
• Add a new "libcef_static_unittests" executable target to support
  light-weight unit tests of libcef_static internals (e.g. without
  requiring exposure via the CEF API). Files to be unittested are
  placed in the new "libcef_static_unittested" source_set which is
  then included by both the existing libcef_static library and the
  new unittests executable target.
• Linux: Remove use_bundled_fontconfig=false, which is no longer
  required and causes unittest build errors (see issue Linux Ubuntu 16.04: Hang during startup in FT_Load_Glyph #2424).

This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the --offline
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.

→ <<cset 0fb8a5f1eada (bb)>>

[magreenblatt]

Add support for direct DevTools protocol messaging (fixes issue #2961).

This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.

This change includes additional supporting changes:

• Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
  callback (see issue Add callback for document element creation #1454).
• Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
• Add a --devtools-protocol-log-file=<path> command-line flag for
  logging protocol messages sent to/from the DevTools front-end
  while it is displayed. This is useful for understanding existing
  DevTools protocol usage.
• Add a new "libcef_static_unittests" executable target to support
  light-weight unit tests of libcef_static internals (e.g. without
  requiring exposure via the CEF API). Files to be unittested are
  placed in the new "libcef_static_unittested" source_set which is
  then included by both the existing libcef_static library and the
  new unittests executable target.
• Linux: Remove use_bundled_fontconfig=false, which is no longer
  required and causes unittest build errors (see issue Linux Ubuntu 16.04: Hang during startup in FT_Load_Glyph #2424).

This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the --offline
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.

→ <<cset fd6631bd1812 (bb)>>