Revert of use log2(scale) to compute mip level (patchset #7 id:120001 of https://codereview.chromium.org/849333002/)

Reason for revert:
need more suppressions

Original issue's description:
> use log2(scale) to compute mip level
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/15fd47f8a07615a7f5d78581aee4c80ff9f17fd9

TBR=robertphillips@google.com,jvanverth@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/856783004

4 files changed, 3 insertions, 37 deletions

diff --git a/expectations/gm/ignored-tests.txt b/expectations/gm/ignored-tests.txt
index 6367eb5009..7bc03a30a5 100644
--- a/expectations/gm/ignored-tests.txt
+++ b/expectations/gm/ignored-tests.txt
@@ -37,17 +37,6 @@
 colortype_xfermodes
 mixed_xfermodes
 
-# reed - rebase after mipmap level improvement
-downsamplebitmap_image_medium_mandrill_512
-downsamplebitmap_image_medium_mandrill_132x132_12x12
-downsamplebitmap_image_medium_mandrill_512.png
-downsamplebitmap_image_medium_mandrill_132x132_12x12.astc
-downsamplebitmap_checkerboard_medium_512_256
-downsamplebitmap_text_medium_72.00pt
-filterindiabox
-coloremoji
-fontmgr_iter
-
 # robertphillips - skia:2995
 blurrects
 
diff --git a/include/core/SkFloatingPoint.h b/include/core/SkFloatingPoint.h
index 9fb343261b..1003b80b4f 100644
--- a/include/core/SkFloatingPoint.h
+++ b/include/core/SkFloatingPoint.h
@@ -91,16 +91,6 @@ static inline float sk_float_copysign(float x, float y) {
     #define sk_float_log(x)         logf(x)
 #endif
 
-// can't find log2f on android, but maybe that just a tool bug?
-#ifdef SK_BUILD_FOR_ANDROID
-    static inline float sk_float_log2(float x) {
-        const double inv_ln_2 = 1.44269504088896;
-        return (float)(log(x) * inv_ln_2);
-    }
-#else
-    #define sk_float_log2(x)        log2f(x)
-#endif
-
 #ifdef SK_BUILD_FOR_WIN
     #define sk_float_isfinite(x)    _finite(x)
     #define sk_float_isnan(x)       _isnan(x)
diff --git a/include/core/SkScalar.h b/include/core/SkScalar.h
index e8c7a7fb65..94c3ce15c0 100644
--- a/include/core/SkScalar.h
+++ b/include/core/SkScalar.h
@@ -58,7 +58,6 @@ typedef float SkScalar;
 #define SkScalarATan2(y, x)         (float)sk_float_atan2(y,x)
 #define SkScalarExp(x)              (float)sk_float_exp(x)
 #define SkScalarLog(x)              (float)sk_float_log(x)
-#define SkScalarLog2(x)             (float)sk_float_log2(x)
 
 #else   // SK_SCALAR_IS_DOUBLE
 
@@ -101,7 +100,6 @@ typedef double SkScalar;
 #define SkScalarATan2(y, x)         atan2(y,x)
 #define SkScalarExp(x)              exp(x)
 #define SkScalarLog(x)              log(x)
-#define SkScalarLog2(x)             log2(x)
 
 #endif
 
diff --git a/src/core/SkMipMap.cpp b/src/core/SkMipMap.cpp
index 2dad6d9c57..83164b1526 100644
--- a/src/core/SkMipMap.cpp
+++ b/src/core/SkMipMap.cpp
@@ -225,7 +225,8 @@ SkMipMap* SkMipMap::Build(const SkBitmap& src, SkDiscardableFactoryProc fact) {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-#ifdef SK_SUPPORT_LEGACY_MIPLEVELCHOICE
+//static int gCounter;
+
 static SkFixed compute_level(SkScalar scale) {
     SkScalar inv = SkScalarAbs(SkScalarInvert(scale));
     if (inv > 32767) {  // Watch out for SkFixed overflow.
@@ -240,29 +241,17 @@ static SkFixed compute_level(SkScalar scale) {
     SkASSERT(clz >= 1 && clz <= 15);
     return SkIntToFixed(15 - clz) + ((unsigned)(s << (clz + 1)) >> 16);
 }
-#endif
 
 bool SkMipMap::extractLevel(SkScalar scale, Level* levelPtr) const {
     if (NULL == fLevels) {
         return false;
     }
 
-    if (scale >= SK_Scalar1 || scale <= 0 || !SkScalarIsFinite(scale)) {
+    if (scale >= SK_Scalar1) {
         return false;
     }
 
-#ifdef SK_SUPPORT_LEGACY_MIPLEVELCHOICE
     int level = compute_level(scale) >> 16;
-#else
-    SkScalar L = -SkScalarLog2(scale);
-    if (!SkScalarIsFinite(L)) {
-        return false;
-    }
-    SkASSERT(L >= 0);
-    int level = SkScalarRoundToInt(L);
-//    SkDebugf("mipmap scale=%g L=%g level=%d\n", scale, L, level);
-#endif
-
     SkASSERT(level >= 0);
     if (level <= 0) {
         return false;