[apps/escher] Fix scroll view indicator margin

So it does not overflow the scrolled view. Fixed for the language
controllers (on boarding app and settings), one value was changed from a
magic 14 to Metric::CommonTopMargin = 15, it did not seem to break
anything.

apps/on_boarding/language_controller.cpp

@@ -1,6 +1,7 @@
 #include "language_controller.h"
 #include "../global_preferences.h"
 #include "../apps_container.h"
+#include <escher/scroll_view_indicator.h>
 #include <algorithm>
 
 namespace OnBoarding {
@@ -11,6 +12,9 @@ LanguageController::LanguageController(Responder * parentResponder) :
     std::max(static_cast<int>(Metric::CommonLeftMargin),
       (Ion::Display::Height - I18n::NumberOfLanguages*Metric::ParameterCellHeight)/2))
 {
+  static_cast<ScrollViewIndicator * >(m_selectableTableView.decorator()->indicatorAtIndex(1))->setMargin(
+      std::max(static_cast<int>(Metric::CommonLeftMargin),
+        (Ion::Display::Height - I18n::NumberOfLanguages*Metric::ParameterCellHeight)/2));
 }
 
 bool LanguageController::handleEvent(Ion::Events::Event event) {

apps/shared/language_controller.h

@@ -23,8 +23,11 @@ public:
   int reusableCellCount() const override;
 
   void willDisplayCellForIndex(HighlightCell * cell, int index) override;
-private:
+
+protected:
   SelectableTableView m_selectableTableView;
+
+private:
   MessageTableCell m_cells[I18n::NumberOfLanguages];
 };
 

escher/src/scroll_view_indicator.cpp

@@ -1,4 +1,5 @@
 #include <escher/scroll_view_indicator.h>
+#include <escher/metric.h>
 #include <escher/palette.h>
 extern "C" {
 #include <assert.h>
@@ -8,7 +9,7 @@ extern "C" {
 ScrollViewIndicator::ScrollViewIndicator() :
   View(),
   m_color(Palette::GreyDark),
-  m_margin(14)
+  m_margin(Metric::CommonTopMargin)
 {
 }