Android Text component allowFontScaling

Summary:
The reason for this change is to implement `allowFontScaling` on the Android's React Native Text component.  Prior to this PR `allowFontScaling` only works for iOS.

The following link contains images of `allowFontScaling` working in Android on small, normal, large, and huge system fonts (from native Android display settings)

http://imgur.com/a/94bF1

The following link is a video of the same thing working on an Android emulator

https://youtu.be/1jTlZhPdj9Y

Here is the sample code snippet driving the video/images
```
render() {
    const size = [12, 14, 16, 18];
    return (
      <View style={{backgroundColor: 'white', flex: 1}}>
        <Text>
          Default size no allowFontScaling prop (default true)
        </Text>
        <Text allowFontScaling={true}>
          Default size allowFontScaling: true
        </Text>
        <Text style={{ marginBottom: 10, }} allowFontScaling={false}>
          Default size allowFontScaling: false
        </Text>

        { size.map(
Closes facebook#10898

Differential Revision: D4335190

Pulled By: lacker

fbshipit-source-id: 0480809c44983644ff2abfcaf4887569b2bfede5

Libraries/Text/Text.js

@@ -153,8 +153,6 @@ const Text = React.createClass({
     /**
      * Specifies whether fonts should scale to respect Text Size accessibility setting on iOS. The
      * default is `true`.
-     *
-     * @platform ios
      */
     allowFontScaling: React.PropTypes.bool,
     /**

ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewProps.java

@@ -83,6 +83,8 @@ public class ViewProps {
   public static final String TEXT_ALIGN_VERTICAL = "textAlignVertical";
   public static final String TEXT_DECORATION_LINE = "textDecorationLine";
 
+  public static final String ALLOW_FONT_SCALING = "allowFontScaling";
+
   public static final String BORDER_WIDTH = "borderWidth";
   public static final String BORDER_LEFT_WIDTH = "borderLeftWidth";
   public static final String BORDER_TOP_WIDTH = "borderTopWidth";

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactTextShadowNode.java

@@ -195,7 +195,9 @@ protected static Spannable fromTextCSSNode(ReactTextShadowNode textCSSNode) {
     buildSpannedFromTextCSSNode(textCSSNode, sb, ops);
     if (textCSSNode.mFontSize == UNSET) {
       sb.setSpan(
-          new AbsoluteSizeSpan((int) Math.ceil(PixelUtil.toPixelFromSP(ViewDefaults.FONT_SIZE_SP))),
+          new AbsoluteSizeSpan(textCSSNode.mAllowFontScaling
+          ? (int) Math.ceil(PixelUtil.toPixelFromSP(ViewDefaults.FONT_SIZE_SP))
+          : (int) Math.ceil(PixelUtil.toPixelFromDIP(ViewDefaults.FONT_SIZE_SP))),
           0,
           sb.length(),
           Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
@@ -305,12 +307,15 @@ private static int parseNumericFontWeight(String fontWeightString) {
 
   private float mLineHeight = Float.NaN;
   private boolean mIsColorSet = false;
+  private boolean mAllowFontScaling = true;
   private int mColor;
   private boolean mIsBackgroundColorSet = false;
   private int mBackgroundColor;
 
   protected int mNumberOfLines = UNSET;
   protected int mFontSize = UNSET;
+  protected float mFontSizeInput = UNSET;
+  protected int mLineHeightInput = UNSET;
   protected int mTextAlign = Gravity.NO_GRAVITY;
 
   private float mTextShadowOffsetDx = 0;
@@ -412,10 +417,26 @@ public void setNumberOfLines(int numberOfLines) {
 
   @ReactProp(name = ViewProps.LINE_HEIGHT, defaultInt = UNSET)
   public void setLineHeight(int lineHeight) {
-    mLineHeight = lineHeight == UNSET ? Float.NaN : PixelUtil.toPixelFromSP(lineHeight);
+    mLineHeightInput = lineHeight;
+    if (lineHeight == UNSET) {
+      mLineHeight = Float.NaN;
+    } else {
+      mLineHeight = mAllowFontScaling ?
+        PixelUtil.toPixelFromSP(lineHeight) : PixelUtil.toPixelFromDIP(lineHeight);
+    }
     markUpdated();
   }
 
+  @ReactProp(name = ViewProps.ALLOW_FONT_SCALING, defaultBoolean = true)
+  public void setAllowFontScaling(boolean allowFontScaling) {
+    if (allowFontScaling != mAllowFontScaling) {
+      mAllowFontScaling = allowFontScaling;
+      setFontSize(mFontSizeInput);
+      setLineHeight(mLineHeightInput);
+      markUpdated();
+    }
+  }
+
   @ReactProp(name = ViewProps.TEXT_ALIGN)
   public void setTextAlign(@Nullable String textAlign) {
     if (textAlign == null || "auto".equals(textAlign)) {
@@ -437,8 +458,10 @@ public void setTextAlign(@Nullable String textAlign) {
 
   @ReactProp(name = ViewProps.FONT_SIZE, defaultFloat = UNSET)
   public void setFontSize(float fontSize) {
+    mFontSizeInput = fontSize;
     if (fontSize != UNSET) {
-      fontSize = (float) Math.ceil(PixelUtil.toPixelFromSP(fontSize));
+      fontSize = mAllowFontScaling ? (float) Math.ceil(PixelUtil.toPixelFromSP(fontSize))
+        : (float) Math.ceil(PixelUtil.toPixelFromDIP(fontSize));
     }
     mFontSize = (int) fontSize;
     markUpdated();