refactor(slider): remove redundant renderer class

Gets rid of the `SliderRenderer` class which doesn't really do much, apart from holding a couple of methods. The methods have been moved into the slider itself.

Author: crisbeto

src/lib/slider/slider.html

@@ -1,4 +1,4 @@
-<div class="mat-slider-wrapper">
+<div class="mat-slider-wrapper" #sliderWrapper>
   <div class="mat-slider-track-wrapper">
     <div class="mat-slider-track-background" [ngStyle]="_trackBackgroundStyles"></div>
     <div class="mat-slider-track-fill" [ngStyle]="_trackFillStyles"></div>

src/lib/slider/slider.ts

@@ -19,6 +19,7 @@ import {
   ViewEncapsulation,
   ChangeDetectionStrategy,
   ChangeDetectorRef,
+  ViewChild,
 } from '@angular/core';
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
 import {coerceBooleanProperty, coerceNumberProperty, HammerInput} from '../core';
@@ -377,9 +378,6 @@ export class MdSlider extends _MdSliderMixinBase
   /** The size of a tick interval as a percentage of the size of the track. */
   private _tickIntervalPercent: number = 0;
 
-  /** A renderer to handle updating the slider's thumb and fill track. */
-  private _renderer: SliderRenderer;
-
   /** The dimensions of the slider. */
   private _sliderDimensions: ClientRect | null = null;
 
@@ -394,6 +392,9 @@ export class MdSlider extends _MdSliderMixinBase
   /** Decimal places to round to, based on the step amount. */
   private _roundLabelTo: number;
 
+  /** Reference to the inner slider wrapper element. */
+  @ViewChild('sliderWrapper') private _sliderWrapper: ElementRef;
+
   /**
    * Whether mouse events should be converted to a slider position by calculating their distance
    * from the right or bottom edge of the slider as opposed to the top or left.
@@ -415,7 +416,6 @@ export class MdSlider extends _MdSliderMixinBase
     this._focusOriginMonitor
         .monitor(this._elementRef.nativeElement, renderer, true)
         .subscribe((origin: FocusOrigin) => this._isActive = !!origin && origin !== 'keyboard');
-    this._renderer = new SliderRenderer(this._elementRef);
   }
 
   ngOnDestroy() {
@@ -429,7 +429,7 @@ export class MdSlider extends _MdSliderMixinBase
 
     // We save the dimensions of the slider here so we can use them to update the spacing of the
     // ticks and determine where on the slider click and slide events happen.
-    this._sliderDimensions = this._renderer.getSliderDimensions();
+    this._sliderDimensions = this._getSliderDimensions();
     this._updateTickIntervalPercent();
   }
 
@@ -439,7 +439,7 @@ export class MdSlider extends _MdSliderMixinBase
     }
 
     this._isSliding = false;
-    this._renderer.addFocus();
+    this._focusHostElement();
     this._updateValueFromPosition({x: event.clientX, y: event.clientY});
 
     /* Emits a change and input event if the value changed. */
@@ -475,7 +475,7 @@ export class MdSlider extends _MdSliderMixinBase
     this._onMouseenter();
 
     this._isSliding = true;
-    this._renderer.addFocus();
+    this._focusHostElement();
 
     if (event) {
       this._updateValueFromPosition({x: event.center.x, y: event.center.y});
@@ -491,7 +491,7 @@ export class MdSlider extends _MdSliderMixinBase
   _onFocus() {
     // We save the dimensions of the slider here so we can use them to update the spacing of the
     // ticks and determine where on the slider click and slide events happen.
-    this._sliderDimensions = this._renderer.getSliderDimensions();
+    this._sliderDimensions = this._getSliderDimensions();
     this._updateTickIntervalPercent();
   }
 
@@ -641,6 +641,23 @@ export class MdSlider extends _MdSliderMixinBase
     return Math.max(min, Math.min(value, max));
   }
 
+  /**
+   * Get the bounding client rect of the slider track element.
+   * The track is used rather than the native element to ignore the extra space that the thumb can
+   * take up.
+   */
+  private _getSliderDimensions() {
+    return this._sliderWrapper ? this._sliderWrapper.nativeElement.getBoundingClientRect() : null;
+  }
+
+  /**
+   * Focuses the native element.
+   * Currently only used to allow a blur event to fire but will be used with keyboard input later.
+   */
+  private _focusHostElement() {
+    this._elementRef.nativeElement.focus();
+  }
+
   /**
    * Sets the model value. Implemented as part of ControlValueAccessor.
    * @param value
@@ -676,33 +693,3 @@ export class MdSlider extends _MdSliderMixinBase
     this.disabled = isDisabled;
   }
 }
-
-/**
- * Renderer class in order to keep all dom manipulation in one place and outside of the main class.
- * @docs-private
- */
-export class SliderRenderer {
-  private _sliderElement: HTMLElement;
-
-  constructor(elementRef: ElementRef) {
-    this._sliderElement = elementRef.nativeElement;
-  }
-
-  /**
-   * Get the bounding client rect of the slider track element.
-   * The track is used rather than the native element to ignore the extra space that the thumb can
-   * take up.
-   */
-  getSliderDimensions() {
-    let wrapperElement = this._sliderElement.querySelector('.mat-slider-wrapper');
-    return wrapperElement ? wrapperElement.getBoundingClientRect() : null;
-  }
-
-  /**
-   * Focuses the native element.
-   * Currently only used to allow a blur event to fire but will be used with keyboard input later.
-   */
-  addFocus() {
-    this._sliderElement.focus();
-  }
-}