[Android] Provide fallback scaling constants in ViewConfiguration

Certain devices may lack the internal Android dimension lookups for
MinScalingSpan and MinScalingTouchMajor.  Provide sensible default backups
for this case.

BUG=345602
NOTRY=true

Review URL: https://codereview.chromium.org/175493002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252641 0039d316-1c4b-4281-b951-d872f2087c98

ui/android/java/res/values/dimens.xml

@@ -15,4 +15,12 @@
     <dimen name="autofill_text_height">44dp</dimen>
     <dimen name="autofill_text_divider_height">1px</dimen>
 
+    <!--
+         Fallback values if the corresponding com.android.internal.R dimensions
+         cannot be retrieved by name.
+         Note: Constants taken directly from Android's core/res/values/config.xml.
+    -->
+    <dimen name="config_minScalingSpan">27.0mm</dimen>
+    <dimen name="config_minScalingTouchMajor">48.0dp</dimen>
+
 </resources>

ui/android/java/resource_map/org/chromium/ui/R.java

@@ -73,5 +73,7 @@ public static final class dimen {
         public static int autofill_text_height;
         public static int autofill_text_divider_height;
         public static int color_button_height;
+        public static int config_minScalingSpan;
+        public static int config_minScalingTouchMajor;
     }
 }

ui/android/java/src/org/chromium/ui/gfx/ViewConfigurationHelper.java

@@ -12,6 +12,7 @@
 
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
+import org.chromium.ui.R;
 
 /**
  * This class facilitates access to ViewConfiguration-related properties, also
@@ -100,14 +101,19 @@ private int getScaledDoubleTapSlop() {
     @CalledByNative
     private int getScaledMinScalingSpan() {
         final Resources res = mAppContext.getResources();
-        final int id = res.getIdentifier("config_minScalingSpan", "dimen", "android");
+        int id = res.getIdentifier("config_minScalingSpan", "dimen", "android");
+        // Fall back to a sensible default if the internal identifier does not exist.
+        if (id == 0) id = res.getDimensionPixelSize(R.dimen.config_minScalingSpan);
         return res.getDimensionPixelSize(id);
+
     }
 
     @CalledByNative
     private int getScaledMinScalingTouchMajor() {
         final Resources res = mAppContext.getResources();
-        final int id = res.getIdentifier("config_minScalingTouchMajor", "dimen", "android");
+        int id = res.getIdentifier("config_minScalingTouchMajor", "dimen", "android");
+        // Fall back to a sensible default if the internal identifier does not exist.
+        if (id == 0) id = res.getDimensionPixelSize(R.dimen.config_minScalingTouchMajor);
         return res.getDimensionPixelSize(id);
     }