Add reg test for http://crbug.com/348821

tests/DashPathEffectTest.cpp

+#include "Test.h"
+
+#include "SkDashPathEffect.h"
+#include "SkWriteBuffer.h"
+
+#define ASSERT(x) REPORTER_ASSERT(r, x)
+
+// crbug.com/348821 was rooted in SkDashPathEffect refusing to flatten and unflatten itself when
+// fInitialDashLength < 0 (a signal the effect is nonsense).  Here we test that it flattens.
+
+DEF_TEST(DashPathEffectTest_crbug_348821, r) {
+    SkScalar intervals[] = { 1.76934361e+36f, 2.80259693e-45f };  // Values from bug.
+    const int count = 2;

[reed1, 2014/03/07 14:52:59]

I *thought* the bug was triggered by count < 0 ...?

[mtklein, 2014/03/07 15:00:10]

Nope.  This is the path effect:

(gdb) p *this
$1 = {
  <SkPathEffect> = {
    <SkFlattenable> = {
      <SkRefCnt> = {
        <SkRefCntBase> = {
          <SkNoncopyable> = {<No data fields>},
          members of SkRefCntBase:
          _vptr$SkRefCntBase = 0xd288648,
          fRefCnt = 2
        },
        members of SkRefCnt:
        flags_ = 1
      }, <No data fields>}, <No data fields>},
  members of SkDashPathEffect:
  fIntervals = 0x7baa61b0,
  fCount = 2,
  fInitialDashLength = -1,
  fInitialDashIndex = 0,
  fIntervalLength = 0,
  fScaleToFit = false
}
(gdb) p (SkScalar[2])this->fIntervals
$2 = {1.76934361e+36, 2.80259693e-45}

I didn't happen to record phase, so here I'm forcing that path with infinity.

+    SkScalar phase = 1.0f/0.0f;  // Used to force the bad fInitialDashLength = -1 path.

[reed1, 2014/03/07 14:52:59]

you may get compiler warnings about this construct.

fyi: we have SK_ScalarInfinity and SK_ScalarNaN for this purpose if you need it.

[mtklein, 2014/03/07 15:00:10]

Duh, right.  Done.

+    SkAutoTUnref<SkDashPathEffect> dash(SkDashPathEffect::Create(intervals, count, phase));
+
+    ASSERT(dash->getFactory() != NULL);  // NULL -> refuses to work with flattening framework.
+
+    SkWriteBuffer buffer;
+    buffer.writeFlattenable(dash);
+    ASSERT(buffer.bytesWritten() > 12);  // We'd write 12 if broken, >=40 if not.
+}