Fix controlling volume slider with keyboard

In the current code base, a float number is used when users try to control
the volume slider by using keyboard. It increases/decreases the volume by
0.1 (or 10%) after each press. In the CL2281173002, it accidentally
changed this increment to an integer, so the volume either jumps to silent
or max.

BUG=631775

Review-Url: https://codereview.chromium.org/2297833002
Cr-Commit-Position: refs/heads/master@{#415700}

ui/views/controls/slider.cc

@@ -242,7 +242,7 @@ void Slider::OnMouseReleased(const ui::MouseEvent& event) {
 }
 
 bool Slider::OnKeyPressed(const ui::KeyEvent& event) {
-  int new_value = value_;
+  float new_value = value_;
   if (event.key_code() == ui::VKEY_LEFT)
     new_value -= keyboard_increment_;
   else if (event.key_code() == ui::VKEY_RIGHT)

ui/views/controls/slider_unittest.cc

@@ -16,6 +16,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/events/event.h"
 #include "ui/events/gesture_event_details.h"
+#include "ui/events/keycodes/keyboard_codes.h"
 #include "ui/events/test/event_generator.h"
 #include "ui/views/test/slider_test_api.h"
 #include "ui/views/test/views_test_base.h"
@@ -302,6 +303,19 @@ TEST_F(HorizontalSliderTest, SliderValueForScrollGesture) {
   EXPECT_NEAR(0.75, slider()->value(), 0.03);
 }
 
+// Test the slider location by adjusting it using keyboard.
+TEST_F(HorizontalSliderTest, SliderValueForKeyboard) {
+  float value =0.5;
+  slider()->SetValue(value);
+  slider()->RequestFocus();
+  event_generator()->PressKey(ui::VKEY_RIGHT, 0);
+  EXPECT_GT(slider()->value(), value);
+
+  slider()->SetValue(value);
+  event_generator()->PressKey(ui::VKEY_LEFT, 0);
+  EXPECT_LT(slider()->value(), value);
+}
+
 // Verifies the correct SliderListener events are raised for a tap gesture.
 TEST_F(HorizontalSliderTest, SliderListenerEventsForTapGesture) {
   test::SliderTestApi slider_test_api(slider());