GrTessellator: fix for points which become non-finite on AA stroking.

If input points are near-infinite, they may become inf or NaN when
stroked.  Before converting the results of intersection from double
to float, clamp them to the [-FLT_MAX/FLT_MAX] range.

BUG=798679

Change-Id: I7d61130dd26147a9b7cfd38aa96567e3867b5c3e
Reviewed-on: https://skia-review.googlesource.com/90983
Commit-Queue: Stephen White <senorblanco@chromium.org>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/tests/TessellatingPathRendererTests.cpp b/tests/TessellatingPathRendererTests.cpp
index 4262945..6368c47 100644
--- a/tests/TessellatingPathRendererTests.cpp
+++ b/tests/TessellatingPathRendererTests.cpp
@@ -406,6 +406,17 @@
     return path;
 }
 
+
+// A path which results in non-finite points when stroked and bevelled for AA.
+static SkPath create_path_27() {
+     SkPath path;
+     path.moveTo(8.5027233009104409507e+37, 1.7503381025241130639e+37);
+     path.lineTo(7.0923661737711584874e+37, 1.4600074517285415699e+37);
+     path.lineTo(7.0848733446033294691e+37, 1.4584649744781838604e+37);
+     path.lineTo(-2.0473916115129349496e+37, -4.2146796450364162012e+36);
+     path.lineTo(2.0473912312177548811e+37, 4.2146815465123165435e+36);
+     return path;
+}
 static std::unique_ptr<GrFragmentProcessor> create_linear_gradient_processor(GrContext* ctx) {
 
     SkPoint pts[2] = { {0, 0}, {1, 1} };
@@ -495,5 +506,6 @@
     test_path(ctx, rtc.get(), create_path_24());
     test_path(ctx, rtc.get(), create_path_25(), SkMatrix(), GrAAType::kCoverage);
     test_path(ctx, rtc.get(), create_path_26(), SkMatrix(), GrAAType::kCoverage);
+    test_path(ctx, rtc.get(), create_path_27(), SkMatrix(), GrAAType::kCoverage);
 }
 #endif