Remove all uses of display:block and display:inline-block.

-Make display:flex, flex-direction: column, flex-shrink: 1 the default.
-Simplify StyleAdjuster::adjustStyleForAlignment to remove special cases we
won't need as we make flex the default and remove absolute positioning.
-Fix a bug this exposed in column flexboxes where we'd apply the wrong edge
of border/padding/margin.
-For now leave the default of align-items:stretch. The main change here is
that iframe/img will do width:auto the same as blocks (i.e. the width of
the parent). I think this is a good change, but we'll have to see how it feels
in practice.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1061163002

examples/stocks/lib/stock_arrow.dart

@@ -10,6 +10,7 @@ class StockArrow extends Component {
     width: 40px;
     height: 40px;
     display: flex;
+    flex-direction: row;
     align-items: center;
     justify-content: center;
     border-radius: 40px;

examples/stocks/lib/stock_row.dart

@@ -11,6 +11,7 @@ import 'stock_data.dart';
 class StockRow extends Component {
   static final Style _style = new Style('''
     display: flex;
+    flex-direction: row;
     align-items: center;
     border-bottom: 1px solid #F4F4F4;
     padding-top: 16px;