DevTools: [SSP] do not liveedit content property of pseudo element matched style

Live-editing "content" property of pseudo element matched style
might result in unfortunate deletion of the element and changing of
selected element in ElementsPanel.

BUG=433889
R=vsevik

Review URL: https://codereview.chromium.org/745543003

git-svn-id: svn://svn.chromium.org/blink/trunk@185788 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [SSP] introduce strict type for style rules

This patch introduces WebInspector.StylesSectionModel which substitutes
untyped style rules in StylesSidebarPane.

R=vsevik

Review URL: https://codereview.chromium.org/740303002

git-svn-id: svn://svn.chromium.org/blink/trunk@185789 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Local variables are not mutable through "Scope Variables" section.

BUG=420399
R=apavlov

Review URL: https://codereview.chromium.org/745603002

git-svn-id: svn://svn.chromium.org/blink/trunk@185790 bbb929c8-8fbe-4397-9dbb-9b2b20218538