ios fixes

skia_ios.mm
Get the app's Documents directory and pass use it to set the resource path.
This is a quick hack which will be replaced by a new application that is
a tiny shim around a command line tool.

SkImageEncoder.h
SkForceLinking.cpp
SkImageDecoder_CG.cpp
Add support for FORCE_LINKING so iOS sees the PNG encoder and others.

SkFloatBits.cpp
SkPoint.cpp
Handle denormalized numbers that are floored by the iOS ARM processor.

SkImageDecoder_iOS.mm
Remove empty encoder factory.

SkTouchGesture.cpp
Return early on empty state on touch rather than aborting (crashing)

JpegTest.cpp
Hal via stackoverflow.com says partial jpegs can be gray as well.

skia_test.cpp
Remove crash handler call for now to avoid link failure.

OverwriteLine.h
Remove fancy line overwrite for iOS.

Resources.cpp
Add interface to set resource directory based on runtime query.

BUG=skia:2736 skia:2737 skia:2738
R=reed@google.com, halcanary@google.com, mtklein@google.com, tfarina@chromium.org

Author: caryclark@google.com

Review URL: https://codereview.chromium.org/373383003
diff --git a/src/core/SkFloatBits.cpp b/src/core/SkFloatBits.cpp
index 39b51ab..6b35a75 100644
--- a/src/core/SkFloatBits.cpp
+++ b/src/core/SkFloatBits.cpp
@@ -85,7 +85,16 @@
         value = SkApplySign(value, SkExtractSign(packed));
         exp = -exp;
         if (exp > 25) {   // underflow
+#ifdef SK_DISCARD_DENORMALIZED_FOR_SPEED
+        // The iOS ARM processor discards small denormalized numbers to go faster.
+        // The comparision below empirically causes the result to agree with the
+        // tests in MathTest test_float_floor
+            if (exp > 149) {
+                return 0;
+            }
+#else
             exp = 25;
+#endif
         }
         // int add = 0;
         return value >> exp;
@@ -145,7 +154,17 @@
         value = SkApplySign(value, SkExtractSign(packed));
         exp = -exp;
         if (exp > 25) {   // underflow
+#ifdef SK_DISCARD_DENORMALIZED_FOR_SPEED
+        // The iOS ARM processor discards small denormalized numbers to go faster.
+        // The comparision below empirically causes the result to agree with the
+        // tests in MathTest test_float_ceil
+            if (exp > 149) {
+                return 0;
+            }
+            return 0 < value;
+#else
             exp = 25;
+#endif
         }
         int add = (1 << exp) - 1;
         return (value + add) >> exp;