Fixes several aero and dark shell issues

[JeffryBooher]

Fixes:

• Aero Glass Menus Flicker incessently  brackets#7222
• [Dark Shell][Core]: There is an extra white line between the title bar and menu bar when resize the window. brackets#5288
• Menu bar disappears until hovered, or only repaints partially - if custom window border theme brackets#6801

Two issues reported by @MartinMa

Adds:

• cef_buffered_dc class for easier implementation of buffered drawing whenever needed
• inactive border drawing state

[MartinMa]

Looks great! 👍 That was very fast 😃

[bchintx]

I know you don't "have" to, but could you add a parameter name, like copy? it'll help make it more obvious that it's the Copy Constructor that you're hiding. You've already done so in your other dark shell class definitions.

[JeffryBooher]

doing so causes an unreferenced formal parameter warning which is treated as an error

[bchintx]

oh? bummer. ok. I guess it's fine then.

[bchintx]

@JeffryBooher Done with initial review. Overall, changes look fine. Couple of nit-picky comments, and one bigger concern w/ the RGB choices.

[JeffryBooher]

@bchintx I changed the color per @larz0 suggestion. Let me know what you think.

[bchintx]

@JeffryBooher Thanks for the misc corrections, and, yes, @larz0 's updated inactive frame color looks better. Still, I have two questions/concerns:

(1) is the 1 pel "white" border around the inactive window an intentional change? IMHO, it's a non-standard Window style, and when it's lit up like that, I keep thinking that that window has focus and is in the middle of a window drag operation or something.

(2) I don't notice this in master, but with your branch, if I click-drag the right window border to resize the window, then I'm seeing a flickering white line across the bottom of the main menu area. It only happens while I'm dragging. As soon as I pause or release the mouse button, the white bar is repainted to the background color correctly. However, so long as I'm drag-resizing, the flickering continues.

[JeffryBooher]

&larz0 what do you want to do about true white tuxedo border?

[JeffryBooher]

@bchintx I didn't notice the dragging issue but will take a look.

[larz0]

@JeffryBooher let's use #3c3f41 for the 1px border.

[JeffryBooher]

@bchintx I'm unable to reproduce the flickering line on Windows 8.1 and my fast machine. I can walk you through debugging it if you have time and want to fix it.

[bchintx]

Confirmed that latest changes fix:

• the menu bar flickering that I reported above when resizing the window frame horizontally
• the menu visibility issue reported in #6801 when changing the PaddedBorderWidth
• not seeing any flickering when moving around the window #7222