Show tooltip below for diff view options

So they are not covering the "Next" link.

Bug: Issue 14769
Change-Id: Iafe55f6c6dd70f4b408c78252634f36f8601b09f
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
index b576896..0f8752d 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
@@ -43,6 +43,9 @@
   @property({type: Boolean})
   saveOnChange = false;
 
+  @property({type: Boolean})
+  showTooltipBelow = false;
+
   private readonly restApiService = appContext.restApiService;
 
   /** @override */
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
index 9943b58..3ebb58f 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
@@ -34,6 +34,7 @@
     id="sideBySideBtn"
     link=""
     has-tooltip=""
+    position-below="[[showTooltipBelow]]"
     class$="[[_computeSideBySideSelected(mode)]]"
     title="Side-by-side diff"
     aria-pressed="[[isSideBySideSelected(mode)]]"
@@ -45,6 +46,7 @@
     id="unifiedBtn"
     link=""
     has-tooltip=""
+    position-below="[[showTooltipBelow]]"
     title="Unified diff"
     class$="[[_computeUnifiedSelected(mode)]]"
     aria-pressed="[[isUnifiedSelected(mode)]]"
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_html.ts b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_html.ts
index 8d69007d..743f905 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_html.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_html.ts
@@ -343,6 +343,7 @@
             id="modeSelect"
             save-on-change="[[!_diffPrefsDisabled]]"
             mode="{{changeViewState.diffMode}}"
+            show-tooltip-below=""
           ></gr-diff-mode-selector>
         </div>
         <span
@@ -355,6 +356,7 @@
               link=""
               class="prefsButton"
               has-tooltip=""
+              position-below=""
               title="Diff preferences"
               on-click="_handlePrefsTap"
               ><iron-icon icon="gr-icons:settings"></iron-icon