Change SkColor4f to RGBA channel order

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2093763003

Review-Url: https://codereview.chromium.org/2093763003
diff --git a/src/core/SkColorShader.cpp b/src/core/SkColorShader.cpp
index 250a367..c610816 100644
--- a/src/core/SkColorShader.cpp
+++ b/src/core/SkColorShader.cpp
@@ -133,10 +133,10 @@
 
 sk_sp<SkFlattenable> SkColor4Shader::CreateProc(SkReadBuffer& buffer) {
     SkColor4f color;
-    color.fA = buffer.readScalar(); // readFloat()
-    color.fR = buffer.readScalar();
+    color.fR = buffer.readScalar(); // readFloat()
     color.fG = buffer.readScalar();
     color.fB = buffer.readScalar();
+    color.fA = buffer.readScalar();
     if (buffer.readBool()) {
         // TODO how do we unflatten colorspaces
     }
@@ -144,10 +144,10 @@
 }
 
 void SkColor4Shader::flatten(SkWriteBuffer& buffer) const {
-    buffer.writeScalar(fColor4.fA); // writeFloat()
-    buffer.writeScalar(fColor4.fR);
+    buffer.writeScalar(fColor4.fR); // writeFloat()
     buffer.writeScalar(fColor4.fG);
     buffer.writeScalar(fColor4.fB);
+    buffer.writeScalar(fColor4.fA);
     buffer.writeBool(false);    // TODO how do we flatten colorspaces?
 }
 
@@ -232,7 +232,7 @@
 void SkColor4Shader::toString(SkString* str) const {
     str->append("SkColor4Shader: (");
 
-    str->append("ARGB:");
+    str->append("RGBA:");
     for (int i = 0; i < 4; ++i) {
         str->appendf(" %g", fColor4.vec()[i]);
     }