Various bubbles have title/content misaligned, or did until people started landing bandaids to fix them; see e.g.  bug 704575 .

The root cause of this looks to be https://codereview.chromium.org/2571613002 , which changed BubbleDialogDelegateView::CreateNonClientFrameView() to call views_delegate->GetDialogFrameViewInsets().  In the current code, this lives in the constructor of BubbleDialogDelegateView, and is the line:

  title_margins_ = views_delegate->GetInsetsMetric(InsetsMetric::DIALOG_TITLE);

This resulted in a behavior change pre-Harmony, because the dialog title's horizontal insets differ from the previous ones used there.  In the nomenclature of the old views constants, we went from using kPanelHorizMargin to kButtonHEdgeMarginNew.  The bubble contents remained using the panel margin, and the panel margin seems more semantically correct to me.

So I think step 1 on this bug is ensuring that the bubble title margins are set to the old values pre-Harmony.  In Harmony, these values (which map to PANEL_CONTENT_MARGIN and DIALOG_BUTTON_MARGIN) are both kHarmonyLayoutUnit, so we'll see no visible effect.

Step 2 is unwinding the various bandaids people have landed when they didn't trace back to fix the real root cause here.  For example:

* https://codereview.chromium.org/2773733002 for  bug 704575  can probably just be reverted
* https://codereview.chromium.org/2800723003 was landed in response to the above but I think does not need to be reverted, it looks like the previous code was newly written after the original problem above and thus was just wrong
* https://codereview.chromium.org/2640593002 was landed in response to the original change; I'm wondering if maybe if this is all fixed, we can unwind this a bit and go back to the idea of not having separate title/contents margins for bubbles
* Maybe other CLs did similar things?  I didn't look; possibly searching for people who call set_title_margins() will turn something up