Throw IOException at source of failing to open a dex file.

Before is:
java.lang.ClassNotFoundException: Didn't find class "GCBench" on path: DexPathList[[zip file "/disk2/dalvik-dev/out/host/linux-x86/framework/GCBench.jar"],nativeLibraryDirectories=[/disk2/dalvik-dev/out/host/linux-x86/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
        Suppressed: java.lang.ClassNotFoundException: GCBench
                at java.lang.Class.classForName(Native Method)
                at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
                at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
                at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
                ... 1 more
        Caused by: java.lang.NoClassDefFoundError: Class "LGCBench;" not found
                ... 5 more
And after is:
java.lang.ClassNotFoundException: Didn't find class "GCBench" on path: DexPathList[[zip file "/disk2/dalvik-dev/out/host/linux-x86/framework/GCBench.jar"],nativeLibraryDirectories=[/disk2/dalvik-dev/out/host/linux-x86/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
        Suppressed: java.io.IOException: Zip archive '/disk2/dalvik-dev/out/host/linux-x86/framework/GCBench.jar' doesn't contain classes.dex
                at dalvik.system.DexFile.openDexFile(Native Method)
                at dalvik.system.DexFile.<init>(DexFile.java:80)
                at dalvik.system.DexFile.<init>(DexFile.java:59)
                at dalvik.system.DexPathList.loadDexFile(DexPathList.java:268)
                at dalvik.system.DexPathList.makeDexElements(DexPathList.java:235)
                at dalvik.system.DexPathList.<init>(DexPathList.java:113)
                at dalvik.system.BaseDexClassLoader.<init>(BaseDexClassLoader.java:48)
                at dalvik.system.PathClassLoader.<init>(PathClassLoader.java:38)
                at java.lang.ClassLoader.createSystemClassLoader(ClassLoader.java:128)
                at java.lang.ClassLoader.access$000(ClassLoader.java:65)
                at java.lang.ClassLoader$SystemClassLoader.<clinit>(ClassLoader.java:81)
                at java.lang.ClassLoader.getSystemClassLoader(ClassLoader.java:137)
        Suppressed: java.lang.ClassNotFoundException: GCBench
                at java.lang.Class.classForName(Native Method)
                at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
                at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
                at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
                ... 1 more
        Caused by: java.lang.NoClassDefFoundError: Class "LGCBench;" not found
                ... 5 more

Also, move dex file verifier messages out of logs.
In the process the ClassLinker::dex_lock_ needed tidying to cover a smaller
scope. Bug 11301553.

Change-Id: I80058652e11e7ea63457cc01a0cb48afe1c15543
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index 6451d5c..00316f7 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -67,7 +67,8 @@
 static void CheckMapRequest(byte*, size_t) { }
 #endif
 
-MemMap* MemMap::MapAnonymous(const char* name, byte* addr, size_t byte_count, int prot) {
+MemMap* MemMap::MapAnonymous(const char* name, byte* addr, size_t byte_count, int prot,
+                             std::string* error_msg) {
   if (byte_count == 0) {
     return new MemMap(name, NULL, 0, NULL, 0, prot);
   }
@@ -82,8 +83,8 @@
   ScopedFd fd(ashmem_create_region(debug_friendly_name.c_str(), page_aligned_byte_count));
   int flags = MAP_PRIVATE;
   if (fd.get() == -1) {
-    PLOG(ERROR) << "ashmem_create_region failed (" << name << ")";
-    return NULL;
+    *error_msg = StringPrintf("ashmem_create_region failed for '%s': %s", name, strerror(errno));
+    return nullptr;
   }
 #else
   ScopedFd fd(-1);
@@ -94,16 +95,17 @@
   if (actual == MAP_FAILED) {
     std::string maps;
     ReadFileToString("/proc/self/maps", &maps);
-    PLOG(ERROR) << "mmap(" << reinterpret_cast<void*>(addr) << ", " << page_aligned_byte_count
-                << ", " << prot << ", " << flags << ", " << fd.get() << ", 0) failed for " << name
-                << "\n" << maps;
-    return NULL;
+    *error_msg = StringPrintf("anonymous mmap(%p, %zd, %x, %x, %d, 0) failed\n%s",
+                              addr, page_aligned_byte_count, prot, flags, fd.get(),
+                              maps.c_str());
+    return nullptr;
   }
   return new MemMap(name, actual, byte_count, actual, page_aligned_byte_count, prot);
 }
 
-MemMap* MemMap::MapFileAtAddress(byte* addr, size_t byte_count,
-                                 int prot, int flags, int fd, off_t start, bool reuse) {
+MemMap* MemMap::MapFileAtAddress(byte* addr, size_t byte_count, int prot, int flags, int fd,
+                                 off_t start, bool reuse, const char* filename,
+                                 std::string* error_msg) {
   CHECK_NE(0, prot);
   CHECK_NE(0, flags & (MAP_SHARED | MAP_PRIVATE));
   if (byte_count == 0) {
@@ -133,10 +135,10 @@
   if (actual == MAP_FAILED) {
     std::string maps;
     ReadFileToString("/proc/self/maps", &maps);
-    PLOG(ERROR) << "mmap(" << reinterpret_cast<void*>(page_aligned_addr)
-                << ", " << page_aligned_byte_count
-                << ", " << prot << ", " << flags << ", " << fd << ", " << page_aligned_offset
-                << ") failed\n" << maps;
+    *error_msg = StringPrintf("mmap(%p, %zd, %x, %x, %d, %lld) of file '%s' failed\n%s",
+                              page_aligned_addr, page_aligned_byte_count, prot, flags, fd,
+                              static_cast<int64_t>(page_aligned_offset),
+                              filename, maps.c_str());
     return NULL;
   }
   return new MemMap("file", actual + page_offset, byte_count, actual, page_aligned_byte_count,