Fix some prevent_unsafe_narrowing warnings

These changes reduce failing targets for skia_unittest when adding
"//build/config/compiler:prevent_unsafe_narrowing" to component("skia")
from 588 to 484 on my local Mac build.

Bug: chromium:1292951
Change-Id: Ice8210e1a2f038feb84184c88e6a34f52168952f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/552376
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Peter Boström <pbos@chromium.org>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>

include/core/SkPaint.h

@@ -256,7 +256,9 @@ public:
     float getAlphaf() const { return fColor4f.fA; }
 
     // Helper that scales the alpha by 255.
-    uint8_t getAlpha() const { return sk_float_round2int(this->getAlphaf() * 255); }
+    uint8_t getAlpha() const {
+        return static_cast<uint8_t>(sk_float_round2int(this->getAlphaf() * 255));
+    }
 
     /** Replaces alpha, leaving RGB
         unchanged. An out of range value triggers an assert in the debug

src/core/SkBlockAllocator.h

@@ -154,7 +154,7 @@ public:
             this->poisonRange(kDataStart, fSize);
         }
 
-        SkDEBUGCODE(int fSentinel;) // known value to check for bad back pointers to blocks
+        SkDEBUGCODE(uint32_t fSentinel;)  // known value to check for bad back pointers to blocks
 
         Block*          fNext;      // doubly-linked list of blocks
         Block*          fPrev;
@@ -403,8 +403,8 @@ public:
     inline BlockIter<false, true> rblocks() const;
 
 #ifdef SK_DEBUG
-    inline static constexpr int kAssignedMarker = 0xBEEFFACE;
+    inline static constexpr uint32_t kAssignedMarker = 0xBEEFFACE;
-    inline static constexpr int kFreedMarker    = 0xCAFEBABE;
+    inline static constexpr uint32_t kFreedMarker = 0xCAFEBABE;
 
     void validate() const;
 #endif

src/core/SkMathPriv.h

@@ -161,7 +161,7 @@ constexpr int SkCLZ_portable(uint32_t x) {
              y = x >>  4; if (y != 0) {n -=  4; x = y;}
              y = x >>  2; if (y != 0) {n -=  2; x = y;}
              y = x >>  1; if (y != 0) {return n - 2;}
-    return n - x;
+    return n - static_cast<int>(x);
 }
 
 static_assert(32 == SkCLZ_portable(0));
@@ -279,12 +279,12 @@ constexpr int SkPrevLog2_portable(uint32_t value) {
  */
 static inline int SkNextPow2(int value) {
     SkASSERT(value > 0);
-    return 1 << SkNextLog2(value);
+    return 1 << SkNextLog2(static_cast<uint32_t>(value));
 }
 
 constexpr int SkNextPow2_portable(int value) {
     SkASSERT(value > 0);
-    return 1 << SkNextLog2_portable(value);
+    return 1 << SkNextLog2_portable(static_cast<uint32_t>(value));
 }
 
 /**
@@ -294,12 +294,12 @@ constexpr int SkNextPow2_portable(int value) {
 */
 static inline int SkPrevPow2(int value) {
     SkASSERT(value > 0);
-    return 1 << SkPrevLog2(value);
+    return 1 << SkPrevLog2(static_cast<uint32_t>(value));
 }
 
 constexpr int SkPrevPow2_portable(int value) {
     SkASSERT(value > 0);
-    return 1 << SkPrevLog2_portable(value);
+    return 1 << SkPrevLog2_portable(static_cast<uint32_t>(value));
 }
 
 ///////////////////////////////////////////////////////////////////////////////

src/gpu/Swizzle.h

@@ -38,7 +38,7 @@ public:
 
     constexpr char operator[](int i) const {
         SkASSERT(i >= 0 && i < 4);
-        int idx = (fKey >> (4U * i)) & 0xfU;
+        int idx = (fKey >> (4 * i)) & 0xfU;
         return IToC(idx);
     }
 
@@ -62,7 +62,7 @@ public:
 private:
     explicit constexpr Swizzle(uint16_t key) : fKey(key) {}
 
-    static constexpr float ComponentIndexToFloat(std::array<float, 4>, int idx);
+    static constexpr float ComponentIndexToFloat(std::array<float, 4>, size_t idx);
     static constexpr int CToI(char c);
     static constexpr char IToC(int idx);
 
@@ -70,7 +70,8 @@ private:
 };
 
 constexpr Swizzle::Swizzle(const char c[4])
-        : fKey((CToI(c[0]) << 0) | (CToI(c[1]) << 4) | (CToI(c[2]) << 8) | (CToI(c[3]) << 12)) {}
+        : fKey(static_cast<uint16_t>((CToI(c[0]) << 0) | (CToI(c[1]) << 4) | (CToI(c[2]) << 8) |
+                                     (CToI(c[3]) << 12))) {}
 
 constexpr Swizzle::Swizzle(const Swizzle& that)
         : fKey(that.fKey) {}
@@ -83,7 +84,7 @@ constexpr Swizzle& Swizzle::operator=(const Swizzle& that) {
 constexpr std::array<float, 4> Swizzle::applyTo(std::array<float, 4> color) const {
     uint32_t key = fKey;
     // Index of the input color that should be mapped to output r.
-    int idx = (key & 15);
+    size_t idx = (key & 15);
     float outR = ComponentIndexToFloat(color, idx);
     key >>= 4;
     idx = (key & 15);
@@ -97,14 +98,14 @@ constexpr std::array<float, 4> Swizzle::applyTo(std::array<float, 4> color) cons
     return { outR, outG, outB, outA };
 }
 
-constexpr float Swizzle::ComponentIndexToFloat(std::array<float, 4> color, int idx) {
+constexpr float Swizzle::ComponentIndexToFloat(std::array<float, 4> color, size_t idx) {
     if (idx <= 3) {
         return color[idx];
     }
-    if (idx == CToI('1')) {
+    if (idx == static_cast<size_t>(CToI('1'))) {
         return 1.0f;
     }
-    if (idx == CToI('0')) {
+    if (idx == static_cast<size_t>(CToI('0'))) {
         return 0.0f;
     }
     SkUNREACHABLE;
@@ -138,11 +139,11 @@ constexpr char Swizzle::IToC(int idx) {
 constexpr Swizzle Swizzle::Concat(const Swizzle& a, const Swizzle& b) {
     uint16_t key = 0;
     for (int i = 0; i < 4; ++i) {
-        int idx = (b.fKey >> (4U * i)) & 0xfU;
+        int idx = (b.fKey >> (4 * i)) & 0xfU;
         if (idx != CToI('0') && idx != CToI('1')) {
             SkASSERT(idx >= 0 && idx < 4);
             // Get the index value stored in a at location idx.
-            idx = ((a.fKey >> (4U * idx)) & 0xfU);
+            idx = ((a.fKey >> (4 * idx)) & 0xfU);
         }
         key |= (idx << (4U * i));
     }

src/gpu/ganesh/GrCaps.h

@@ -352,7 +352,7 @@ public:
 
     size_t bufferMapThreshold() const {
         SkASSERT(fBufferMapThreshold >= 0);
-        return fBufferMapThreshold;
+        return static_cast<size_t>(fBufferMapThreshold);
     }
 
     /** True in environments that will issue errors if memory uploaded to buffers

src/gpu/ganesh/GrMemoryPool.h

@@ -113,7 +113,7 @@ private:
         int fID;       // ID that can be used to track down leaks by clients.
 #endif
 #if defined(SK_DEBUG) || defined(SK_SANITIZE_ADDRESS)
-        int fSentinel; // set to a known value to check for memory stomping; poisoned in ASAN mode
+        uint32_t fSentinel; // set to a known value to check for memory stomping; poisoned in ASAN mode
 #endif
     };