Not all data are displayed by bar graph

**Problem Description**
With creating simple bar plot with chaco strange behavior is occured: half of plot is filled with line_color, another one with fill_color and the last one is not drawn at all (view screenshot). With using small values it works fine (for example using 50 instead of 150 for y values).

**Reproduction Steps:**
Start program

```python

from enable.api import ComponentEditor
from traits.api import Instance, HasStrictTraits
from traitsui.api import View, UItem
from chaco.api import Plot, ArrayPlotData

class TestPlot(HasStrictTraits):
plot = Instance(Plot)
traits_view = View(UItem('plot', editor=ComponentEditor()),
width=1000, height=800, resizable=True,)

def __init__(self, **kw):
super(TestPlot, self).__init__(**kw)

plot_data = ArrayPlotData(x=list(xrange(0, 7000)), y=[150] * 7000)
self.plot = Plot(plot_data)
self.plot.plot(('x', 'y'), type='bar', line_color="gray", fill_color="lightgray")

self.plot.index_mapper.range.set(low=0 - 150, high=8000 + 50)
self.plot.value_mapper.range.set(low=0 - 50, high=100 + 100)

test = TestPlot()

if __name__ == "__main__":
test.configure_traits()
```

**Expected behavior:**
Data from 0 to 7000 for x and from 0 to 150 for y should be displayed and filled with line_color

**OS, Python version:**
Win7, python 2.7