chrome: define markdown key bindings for gmail-message-mode

layers/+lang/markdown/config.el

@@ -34,3 +34,6 @@
     )
   "List of language names or lists of language and mode names for which to
 generate mmm classes.")
+
+(defvar markdown--key-bindings-modes '(markdown-mode gfm-mode)
+  "Modes using markdown key bindings.")

layers/+lang/markdown/packages.el

@@ -75,7 +75,7 @@
          'markdown-mode (car prefix) (cdr prefix)))
       ;; note: `gfm-mode' is part of `markdown-mode.el' so we can define its key
       ;; bindings here
-      (dolist (mode '(markdown-mode gfm-mode))
+      (dolist (mode markdown--key-bindings-modes)
         (spacemacs/set-leader-keys-for-major-mode mode
           ;; Movement
           "{"   'markdown-backward-paragraph

layers/+tools/chrome/packages.el

@@ -13,6 +13,7 @@
                         edit-server
                         gmail-message-mode
                         flymd
+                        markdown-mode
                         ))
 
 (defun chrome/init-edit-server ()
@@ -33,3 +34,9 @@
     :defer t
     :init (setq flymd-browser-open-function
                 'spacemacs//flymd-browser-function)))
+
+(defun chrome/pre-init-markdown-mode ()
+  (spacemacs|use-package-add-hook markdown-mode
+    :pre-config
+    (when (configuration-layer/package-usedp 'gmail-message-mode)
+      (add-to-list 'markdown--key-bindings-modes 'gmail-message-client-mode))))