[omnibox] Set dimensions of tab switch button before measuring

We were measuring the tab switch button size before setting all the
relevant aspects. When we requested a size, it was therefore too big.
This corrects that and, since the size is more appropriate, we don't
need the left justification, which was broken when there wasn't any
text anyways.

Bug: 780835
Change-Id: I72bd6aedc84837864dc6fe764e4ce865f9170cb4
Reviewed-on: https://chromium-review.googlesource.com/1108452Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Kevin Bailey <krb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569670}

chrome/browser/ui/views/omnibox/omnibox_tab_switch_button.cc

@@ -37,7 +37,7 @@ OmniboxTabSwitchButton::OmniboxTabSwitchButton(OmniboxPopupContentsView* model,
            gfx::CreateVectorIcon(omnibox::kSwitchIcon,
                                  GetLayoutConstant(LOCATION_BAR_ICON_SIZE),
                                  gfx::kChromeIconGrey));
-  SetHorizontalAlignment(gfx::ALIGN_LEFT);
+  SetImageLabelSpacing(8);
   if (!calculated_widths_) {
     icon_only_width_ = MdTextButton::CalculatePreferredSize().width();
     SetText(l10n_util::GetStringUTF16(IDS_OMNIBOX_TAB_SUGGEST_SHORT_HINT));
@@ -51,7 +51,6 @@ OmniboxTabSwitchButton::OmniboxTabSwitchButton(OmniboxPopupContentsView* model,
   set_corner_radius(CalculatePreferredSize().height() / 2.f);
   animation_->SetSlideDuration(500);
   SetElideBehavior(gfx::FADE_TAIL);
-  SetImageLabelSpacing(8);
 
   SetInstallFocusRingOnFocus(true);
   focus_ring()->SetHasFocusPredicate([](View* view) {