Manually set fFilterValues in SkConvolutionFilter1D.

src/core/SkConvolver.cpp

Index: src/core/SkConvolver.cpp
===================================================================
--- src/core/SkConvolver.cpp	(revision 13679)
+++ src/core/SkConvolver.cpp	(working copy)
@@ -283,6 +283,7 @@
         firstNonZero++;
     }
 
+    int initialOffset = fFilterValues.count();
     if (firstNonZero < filterLength) {
         // Here we have at least one non-zero factor.
         int lastNonZero = filterLength - 1;
@@ -294,9 +295,13 @@
         filterLength = lastNonZero + 1 - firstNonZero;
         SkASSERT(filterLength > 0);
 
+        // Calling fFilterValues.reset(), or push_back() in a loop, are expensive.
+        // Over-allocate so we can do it once instead of iteratively.
+        if (!initialOffset) fFilterValues.resize_back(filterLength * filterLength);
         for (int i = firstNonZero; i <= lastNonZero; i++) {
-            fFilterValues.push_back(filterValues[i]);
+            fFilterValues[initialOffset + i - firstNonZero] = filterValues[i];
         }
+
     } else {
         // Here all the factors were zeroes.
         filterLength = 0;