Turn on -Wrange-loop-analysis.

-Wrange-loop-analysis triggers when we use a new-style for loop in a way that appears to unintentionally call a copy constructor on each non-trivial loop element instead of operating on them by reference.


BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4000

Change-Id: If9e1b7fcc1f2789ae03c41c17abb17e60d564a8b
Reviewed-on: https://skia-review.googlesource.com/4000
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

gn/BUILD.gn

@@ -284,7 +284,6 @@ config("warnings") {
       ]
       cflags_cc += [
         "-Wno-abstract-vbase-init",
-        "-Wno-range-loop-analysis",
         "-Wno-weak-vtables",
       ]
 

src/sksl/SkSLCompiler.cpp

@@ -249,8 +249,8 @@ void Compiler::scanCFG(CFG* cfg, BlockId blockId, std::set<BlockId>* workList) {
 // is initially unknown
 static std::unordered_map<const Variable*, const Expression*> compute_start_state(const CFG& cfg) {
     std::unordered_map<const Variable*, const Expression*> result;
-    for (const auto block : cfg.fBlocks) {
-        for (const auto node : block.fNodes) {
+    for (const auto& block : cfg.fBlocks) {
+        for (const auto& node : block.fNodes) {
             if (node.fKind == BasicBlock::Node::kStatement_Kind) {
                 const Statement* s = (Statement*) node.fNode;
                 if (s->fKind == Statement::kVarDeclarations_Kind) {

tests/FontMgrTest.cpp

@@ -690,7 +690,7 @@ static void test_matchStyleCSS3(skiatest::Reporter* reporter) {
     };
 
     for (StyleSetTest& test : tests) {
-        for (const StyleSetTest::Case testCase : test.cases) {
+        for (const StyleSetTest::Case& testCase : test.cases) {
             SkAutoTUnref<SkTypeface> typeface(test.styleSet.matchStyle(testCase.pattern));
             if (typeface) {
                 REPORTER_ASSERT(reporter, typeface->fontStyle() == testCase.expectedResult);