Roll Observatory deps (charted -> ^0.3.0)

packages/charted/lib/core/scales/linear_scale.dart

 //
 // Copyright 2014 Google Inc. All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 //
 part of charted.core.scales;
 
 class LinearScale implements Scale {
@@ skipping 22 matching lines @@
         _rounded = source._rounded {
     _reset();
   }
 
   void _reset({bool nice: false}) {
     if (nice) {
       _domain = ScaleUtils.nice(
           _domain, ScaleUtils.niceStep(_linearTickRange().step));
     }
 
-    Function linear = math.min(_domain.length, _range.length) > 2 ?
-        ScaleUtils.polylinearScale : ScaleUtils.bilinearScale;
+    Function linear = math.min(_domain.length, _range.length) > 2
+        ? ScaleUtils.polylinearScale
+        : ScaleUtils.bilinearScale;
 
     Function uninterpolator = clamp ? uninterpolateClamp : uninterpolateNumber;
     InterpolatorGenerator interpolator =
         _rounded ? createRoundedNumberInterpolator : createNumberInterpolator;
 
-    _invert =
-        linear(_range, _domain, uninterpolator, createNumberInterpolator);
+    _invert = linear(_range, _domain, uninterpolator, createNumberInterpolator);
     _scale = linear(_domain, _range, uninterpolator, interpolator);
   }
 
   @override
   set range(Iterable value) {
     assert(value != null);
     _range = value;
     _reset();
   }
 
@@ skipping 66 matching lines @@
   @override
   num scale(num value) => _scale(value);
 
   @override
   num invert(num value) => _invert(value);
 
   Range _linearTickRange([Extent extent]) {
     if (extent == null) {
       extent = ScaleUtils.extent(_domain);
     }
-    var span = extent.max - extent.min,
-        step =
-            math.pow(10, (math.log(span / _ticksCount) / math.LN10).floor()),
-        err = _ticksCount / span * step;
+    var span = extent.max - extent.min;
+    if (span == 0) {
+      span = 1.0; // [span / _ticksCount] should never be equal zero.
+    }
+    var step = math.pow(10, (math.log(span / _ticksCount) / math.LN10).floor());
+    var err = _ticksCount / span * step;
 
     // Filter ticks to get closer to the desired count.
     if (err <= .15) {
       step *= 10;
-    }
-    else if (err <= .35) {
+    } else if (err <= .35) {
       step *= 5;
-    }
-    else if (err <= .75) {
+    } else if (err <= .75) {
       step *= 2;
     }
 
     return new Range((extent.min / step).ceil() * step,
         (extent.max / step).floor() * step + step * 0.5, step);
   }
 
   @override
   FormatFunction createTickFormatter([String formatStr]) {
     int precision(value) {
       return -(math.log(value) / math.LN10 + .01).floor();
     }
     Range tickRange = _linearTickRange();
     if (formatStr == null) {
       formatStr = ".${precision(tickRange.step)}f";
     }
     NumberFormat formatter = new NumberFormat(new EnUsLocale());
     return formatter.format(formatStr);
   }
 
   @override
   LinearScale clone() => new LinearScale._clone(this);
 }