Fix divide-by-zero in program cache tracking

src/gpu/gl/GrGpuGL_program.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGpuGL.h"
 
 #include "GrEffect.h"
@@ skipping 15 matching lines @@
 #endif
 {
 }
 
 GrGpuGL::ProgramCache::~ProgramCache() {
     // dump stats
 #ifdef PROGRAM_CACHE_STATS
     SkDebugf("--- Program Cache ---\n");
     SkDebugf("Total requests: %d\n", fTotalRequests);
     SkDebugf("Cache misses: %d\n", fCacheMisses);
-    SkDebugf("Cache miss %%: %f\n", (float)fCacheMisses/(float)fTotalRequests);
+    SkDebugf("Cache miss %%: %f\n", (fTotalRequests > 0) 
+                                    ? (float)fCacheMisses/(float)fTotalRequests : 0.0f);
     SkDebugf("---------------------\n");
 #endif
 }
 
 void GrGpuGL::ProgramCache::abandon() {
     for (int i = 0; i < fCount; ++i) {
         GrAssert(NULL != fEntries[i].fProgram.get());
         fEntries[i].fProgram->abandon();
         fEntries[i].fProgram.reset(NULL);
     }
@@ skipping 257 matching lines @@
                          GrGLProgram::kAttribLayouts[attribType].fCount,
                          GrGLProgram::kAttribLayouts[attribType].fType,
                          GrGLProgram::kAttribLayouts[attribType].fNormalized,
                          stride,
                          reinterpret_cast<GrGLvoid*>(
                          vertexOffsetInBytes + vertexAttrib->fOffset));
     }
 
     attribState->disableUnusedAttribArrays(this, usedAttribArraysMask);
 }